within the 4E paradigm, the valid question is, "What role is Bob the Magus?" The idea that he might not act as a striker/controller/defender/leader never occurs (maybe he's a scout), or that he might fit one of those labels now and another in ten minutes and another tomorrow, or that he might fit two or more simultaneously (5E fighters are strikers + defenders simultaneously).
This looks like an empirical claim. What is your evidence?
I haven't done any sort of survey of 4e players. So I can only talk about my own experiences. In my 4e game we have a character who is a defender/controller - a polearm fighter. He also has a dash of leader (good self-heaing via Dwarven second wind plus a bit of party healing also). We have a character who is a leader/striker - a hybrid ranger-cleric. We have a character who is an AoE striker with strong secondary control (mostly via forced movement) and leader (a sorcerer with various sorts of party buffs resulting from Demonskin Adept plus multi-class bard). We have a defender who also provides leader abilities - buff, debuff and healing (a CHA-paladin with Eye for and Eye and similar encounter power responses to attacks against fellow party members).
We also have a character who according to the label is a controllers (invoker with wizard multi-class) but who is generally the weakest character in combat (though he does have some nice AoE debuff when he pulls it out), and whose main function in the party is to be the skill monkey, linguist and ritualist.
So based on my experience, I don't give much credence to these claims about a "4e paradigm" in which characters can't be conceived of except as operating within certain singular roles.
your character could determine the shape of the battlefield depending on where he stands, who he attacks, etc. Move into the center of the enemy forces and split them, now your allies can attack one set together. Stand in a doorway and allow your ranged and spell casters to fire past you.
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with 4e roles, we are talking about characters designed and built to fulfill certain combat tactics every time.
With a doorway, you might act as a controller. Without it, you might action surge and be a striker. You are absolutely right that a thief might decide to hold the doorway and be the controller. Or a wizard might buff his AC and hold the door while you fire or jab with a reach weapon past him.
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But once delineated in the rules and mechanics of the game, you can't play without them.
More empirical claims. What is the evidence?
What, in 4e, stops a sorcerer from buffing up and holding a doorway? Nothing! - and the sorcerer in my 4e game is known for moving into the thick of things from time-to-time.
If we move the focus from playing the game to building PCs, what do you mean by "delineated in the rules and mechanics of the game"? The action resolution rules of 4e don't make reference to roles. Nor do the PC build rules - the roles are labels that serve as guidelines for players who are wondering what their PC might be good at. They are not part of the build mechanics.
In mechanical terms, playing a class labelled "striker" means having build options that tend to support damage dealing and mobility. The "controller" label signals build options that tend to support condition-imposition and forcing movement. The "leader" lablel signals build options that tend to support healing and buffing, as well as perhaps debuffing enemy attacks and/or defences.
"Defender" is discussed in more detail below, but the basics of being a defender in 4e is being able to endure attacks (good AC, good hit points - this has been the fighter for the whole of D&D's history) and about being able to lock down opponents in melee. In 4e being a defender does not of necessity imply low-damage. Fighters are not particularly low-damage. Nor is the paladin in my 4e game. Swordmages often tend to be.
In AD&D achieving melee lockdown did not depend upon build options, but rather was achieved via punitive rules for withdrawing from melee. In 4e lockdown is achieved by more intricate rules around marking and other condition imposition (eg prone, dazed), forced movement, and OAs/interrupts, and access to these mechanical optoins is achieved via fetures of PC build; classes labelled "defender", in particular, provide build options along these lines. (The borderline between "defender" and "controller" is therefore very blurry - in my experience, a high level fighter with access to multiple encounter power AoEs and solid feat-driven debuff with the mobility to get where s/he needs to be is equally well described as a controller as a defender.)
Lewis Pulsipher, one of the leading figures in the late 70s and early 80s British D&D scene (he wrote frequently for the White Dwarf of that period) had an essay in which he set out possible roles for the D&D character classes. For thief this incuded "commando" (= striker, in 4e parlance) and for wizard this included artillery (= AoE striker, in 4e parlance) and anti-personnel via charms, hold etc (= controller, in 4e parlance). He had more roles than the 4e ones, because he mixed-and-matched combat and non-combat functions, whereas in 4e the language of "role" pertains almost exclusively to combat function. (Not completely exclusively - striker, in particular, tends to imply a reasonable degree of mobility, which then tends to imply a scout/movement capability for non-combat exploration.) But it was clear to him that the framework of character classes with varying class features and abilities means that some classes are more easily built to perform certain functions than other classes.
5e still has mechanical build options, and hence there are still some characters who do more damage than others (compare a fighter with a two-handed sword compared to a longsword); some characters who have more access to healing than others (compare a champion fighter to a cleric); some characters who have more access to condition-imposition (compare most wizards to a champion fighter). Furthermore, choice of class continues to be an important factor in framing these choices (eg wizards get more choices for debuffing, clerics and bards get more choices for healing).
Describing 5e's choices in terms of 4e's roles (striker, controller, etc.) would be a step backwards, because the construction of the game makes such roles dependent on circumstances, NOT character build! Any 5e character can be a striker... and then a controller in the next encounter.
A description (I think "label" is actually a better word) doesn't change the thing labelled. You can label a 5e fighter whatever you want - but how does a 5e fighter built per the Basic PDF act as a controller in open terrain - eg where are the AoE debuff options? Or as a healer of any significance? By labelling the class "striker" I indicate that, if you build your character along the lines set out in the PDF, what you will get is a PC whose main ability is to deal damage, but whose ability to force movement, impose conditions/debuff, or heal, is pretty limited.
And I think that would be a rather accurate label for a Basic PDF fighter.
"Strikers specialize in dealing high amounts of damage to a single target at a time,"
I don't know where you got this from, but I don't think it has much bearing on 4e. For instance, the PHB2 labels the sorcerer as a striker (and correclty so, in my experience of seeing a sorcerer in play), and a sorcerer can be built with mostly AoE attacks.
The ranger in my 4e group is a single target striker. He plays pretty differently from the sorceer. (Including getting into the thick of things much less often.)
So does that mean you are right and the
DnD4 wikia is wrong? "A character with the defender role primarily focuses enemy fire by making it difficult for enemies to move past, and punishing enemies who attack other party members." Because your definition implies that the defender
must have the highest offensive output in the game or else a way to make enemies behave irrationally. Where does your definition come from and why should it be preferred?
If Dnd4 wikia is where you got your definition of "striker" then it is not very good. Who wrote it?
I don't know how familiar you are with 4e, but have you actually looked at how 4e defenders work, mechanically?
As others have pointed out upthread, the 43 fighter, for instance, has the following features:
*good AC and hit points, which means that being in the thick of melee is not a hindrance in the way that it is for a wizard or thief (this is true to fighters right back to the origins of D&D);
*a bonus to hit with OAs, which also end the movement of a moving target (this is part of the lockdown, which replicates in 4e the stickiness of melee that in AD&D was achieved via punitive withdrawal rules - 3E was the edition of D&D which, via the 5' step, lost the stickiness of melee);
*the ability to impose a mark on any target who is attacked (whether or not the attack hits) that lasts for one round (a mark is a debuff - it imposes a -2 penalty to attacks that don't target the fighter who imposed it - I think there may be similar mechanics in 3.5, but not in 3E or AD&D);
*the ability to take an immediate action (= 5e reaction, roughly) attack against a marked target who makes an attack that doesn't target the fighter who imposed the mark, or against a marked target who tries to withdraw from the fighter via 5' step (this has a more technical definition using 4e mechanical vocabulary, but I've given the gist of it).
The fighter doesn't "focus enemy fire" in any literal sense - given that "fire" means "ranged attacks", the more the enemy has "fire" the less impact the fighter has on the ingame situation, because s/he has rather limited ranged attacks and hence can't impose marks against targets at range - and even if the marks are imposed, they can't be enforced via immediate actions, because these are triggered only via an adjacent enemy. Using the language of 4e encounter design, if the GM wants to build an encounter that will reduce the impact of the fighter, s/he would include a high proportion of
artillery creatures.
The way the fighter in my 4e game plays is by moving into the middle of the enemy combatants (he has a skill power called Mighty Sprint to help with this) and then laying into them with AoEs (these have no AD&D equivalent, but in 3E terms resemble Whirlwind Attacks). By marking the creatures, the fighter makes it very hard for them to break out of melee: if they try and move, they take an OA which if it hits, stops them; if they try a 5' step as their movement option, they take an attack from the fighter (sometimes called "punishment for mark violation" or "mark enforcement") and have to then choose between forfeiting their attack to move again, or else being not very far away from the fighter but (if the fighter hit with the free attack) being somewhat lower in the hit point department.
At a high level of description the dynamic, in play, is roughly similar to AD&D melees in which, once you go in, only the last person comes out alive - but with much more granular resolution than AD&D, played out via the movement rules, the mark rules, the immediate action rules, etc.
As other posters have indicated upthread, other defenders have different styles. For instance, the paladin has the hit points and AC of a fighter, but uses a different mechanic for marking which makes it harder to mark multiple opponents, but inflicts damage directly on an enemy (without needing to roll an attack) if that enemy makes an attack that doesn't target the paladin.
A paladin also has trouble maintaing and enforcing marks at range, so it would be inaccurate to say that a paladin encourages "focus fire". A paladin's strength is single-target melee lockdown. THis is, overall, weaker defending than a fighter (in my view) but the paladin has other class features to make up for it, like healing and limited buffing.
that also misses 80% of the Hulk concept, which is everything related to the manner in which he does that damage: by smashing people's faces in with raw strength.
As you are using it here, "concept" seems to mean something like "fictional trappings". In the language of roles, fictional trappings are not very relevant. For instance, the fighter controller in my 4e game uses a polearm. The invoker and sorcerer use magic. These differences within the fiction are relevant to various aspects of play, and of resolution, but don't bear upon the
role of the character, which is about function and effect rather than fictional means.
Because almost none of them actually play the defender role. Superman is the sole one who typically plays it.
Thing? Colossus? Hulk? These are not defensive characters.
It's a long time since I've thought about, or read, the FF - but Colossus absolutely plays a defensive role, in the sense that he powers up and soaks gunfire while other X-Men take cover behind him.
It is hard to compare this directly to 4e, though, because 4e (consistent with earlier versions of D&D) tends to treat melee as the true heart of combat. I think quite a bit of work would be needed to build rules for 4e that centred ranged attacks as the core of the game's combat.
I think the OP may have missed a few, including:
Summoner: the guy who can generate disposable minions when needed (e.g. fighting undead with level drain).
Diviner: the guy who can uncover arcane knowledge via scrying and Speak With Dead. Invaluable when solving murders.
Hacker: the guy who can penetrate/shut down/take control of enemy defensive systems. Not a stereotypical D&D activity but this is basically what Abjurors with Counterspell/Dispel Magic are doing
If anyone has told you that these sorts of activities are not feasible objects of specialisation in 4e, you've been misinformed.
Generating disposable minions in 4e is strictly limited, because of the possibility for action economy rorts (which 3E illustrated with its animal companion-basd classes), but various PC builds have various capabilities to do this (eg the invoker/wizard in my game can summon an imp familiar). There are a number of pathways to this in 4e PC building - most of them go under the controller label, but that is not the only way to do it.
A diviner is an out-of-combat role. In 4e this is about ritual capabilities, and so is mostly independent of class, although a few classes (eg invoker, wizard, cleric, druid, psion) get a head start.
A "hacker" in your sense straddles out-of-combat and in-combat. In 4e this is about having good skill checks in apposite skills. A fighter will often struggle a bit with this, as may a ranger (they don't have good skill/stat synergies for the knowledge and social skills this involves) but there are many, many viable pathways. In my 4e game the invoker/wizard is the one who principally serves this function.