I have been thinking along the same lines as Old Gumphrey for a while. I have played a few LFR sessions with 4 strikers & its fun & edgy.
I have a feeling it works better in smaller parties than bigger ones - the bad guys can focus fire better with more of them which can overload the strikers more. The DM can focus tactically, to drop one guy in a given encounter, or strategically, to drain one guy of surges way before the others - though this is somewhat metagaming.
It takes me back to City Of Heroes days (not that 4e is like an MMO

) where my favourite team was a tank, a leader & the rest DPS.
There were debates in that game on whether a second tanker (4e defender) was ever wanted and if even the first was simply a self fullfilling prophecy.
In that game all defenders (4e Leader) was a viable team as they had massive stacking buffs. It has lead me to look at all warlord parties (who are the most offensive leaders) & they look pretty viable (if really dull & probably broken) too.
Interesting..
years ago I played a magician in Everquest (pretty dman good one too!

)
most groups consisted of, at higher level, approximately:
a tank, prefferably a fighter (though a GOOD paladin was ok, paladins were kinda sucky in Everquest for a long time)
A cleric (only clerics had sufifcien theals to be good enough, unless you had a damn good druid and party to back them up)
the rest damage dealers, and be nice if you had a monk or good Shadow Knight for a "Puller" and "snarer" (like Slow in 4th ed, so runners couldn't aggro a mass of enemies onto you, necromancers , wizards and rangers could snare)
alas, the game became stupid in that you HAD ot have either that exact set up because it was insanely hard (creatures that could kill the best fighter in say 2 "rounds", and anyone else in 1!!!)...OR you had to have th every damn best folk there were. "Ordinary Joe" Paladin or whateverm was no use in hard bit sof gates of Discord as they'd get ganked, and that sucked
My class, magician, wwas the best DPs in game (though in long fights, say a god, necros were even better), most folk just never knew it for a long time, until it finally dawned on them, duh!!
For anyone not familiar with the term: DPS = damage per second, reffering in this case to high damage dealing classes (yes I know most ENWorlders are saavy...but acronyms suck...not everyone knows everyhting, hehe)
We found, in Everquest, that it was FAR more profitable, to have a hellishly high DPs group, to whittle down a mob faster than it coudl kill the tank and thus, eat all of us in 1/35th of a second!
interesting points though:
Only fighters, good paladins and magician elemental pets could tank a mob, and the pets weren't so great at it, but were disposable, if Jibober dies, big deal, summon a new one! *hugs his loyal Jibobers!*
If things screwed up, you could send a pet to tank when the fighter died, or an uncontrollable additional critter came.
A "controller", in this case mostly an enchanter (but a really good bard could do it) was usually VITAL. Only two classes could cast the 3.5 ed type of Slow, slowing down enemy damage out put, was onlyw ay you could survive their insane damage. So you'd slow 'em down, and DPs 'em to death toot sweet!
The cleric would hit the tank with a heal over time spell, a super regeneration, as mob came in, the tank woudl taunt the hell out of the mob so it wouldn't kill the cleric for that (heals were huge aggro, which is fair)
An enchanter or shaman would slow it, and then rest of us would light the SOB up like a mushroom cloud! Muhaha
We did work out some interesting combos.
It was better for the enchanter ot be doing some ueful damage, rather than just stand doing nothing, so they'd use charmed beasties
(dear gods were they SICK damage, as NPC vs PC damage was totally
totally out of whack and broken, so a charmed beastie could kill another mob as fast as they could kill us...so the developers had to nerf the damage of charmed mobs, blech!)
Another thing some enchanters but also magicians like me, wizards or necros did, was to use weapons with a nasty "proc"
(Proc = a chance of an effect going off on a strike), there were a handful of weapons in the game casters could use that had unresistbale procs...now this is where it got fun.
An enchanter could cast haste, AND buff Dexterity (which increased the chance to proc), Shamans could buff physical stats the most.
Only the caster proc weapons had powerful damage procs (as balance for our lousy melee ability, they were menat as oh gimmicks, joke, fun items only)
And catsers could take "feats" (AA Abilities) that could increase spell damage and chance to crit, including the procs from these staffs and rods....
So, you'd see several casters whaling the tar out of the monster's backside, as a fight went on, hehe.
Attack from the rear so you'd not get a chance of a riposte from critters that could do damage = to 1/4 to 1/2 your health in 1 hit....
Also, if you aggroed the enemy, it wouldn't run all over chasing your dumb ass, so the tank had less trouble aggroing it back onto himself.
Worked out pretty good

A buffed up caster with right abilities could actually do pretty useful damage with procs alone, and it was also FUN!
(Alas, I never got the Kelp Hilted Mace, as few folk had the guts to fight in the Plane of Water, wussies!)
However, without the lack of a "controller", you were in deep toruble if things went wrong.
You could "control" fights several ways actually, but due to creatures being able ot summon YOU if you damaged them just a few percent (damn what a dumb thing that was, understandable as it was needed to stop cheating, but stupid as it was becuase the NPCs' AI was abyssmal), it was usually far better ot let an enchanter "mesmerize" them.
You could also get a wizard to root & snare them, tricky though, and necromancers snares did damage so they had to use very low level snare spells for safety.
Ideally, you'd have mobs pulled in in a chain fahsion, wiht 1 sitting mesmerized, then slowed, and further debuffed while you killed a previous mob, and hte puller woudl rush out to go get another mob, so you had 3 onthe go all the time, incoming, killing, and mesmerized for ma effciency.
Again, very dumb from a true RPG sense I know, but talking effciency (it's also boring lol, hence "the grind" is the sucky problem with MMOs).
Before NPCs got so stupidly powerful, it was easy to just set a necormancer or magician pet onto additonal creatures to keep them busy and heal the pet as need.
But, sometimes, usually before the NPCs got so powerful, we'd do things different...
AOE Groups were my fave, dangerous as hell but fun!
you'd get a group of casters able to do "close burst" type nukes, so that was primarily wizards, and then to a lesser extent, magicians, plus a healer (prefferably cleric , for rezzing the dead!), an an enchnater (for point blank stuns)
now you could let a bard pull (they are amazing at it!), or let the cleric (they had a sort of short duration invulnerability power that made it excellent)...maybe a necro for summoning dead PCs corpses, help etc.
You'd pull tons of monsters at one go to the group then stun and NUKE them hell out of 'em, mad, barking mad, but what a rush!
*Was in first group on Karana server to AOE the Shrezra Temple, booyah!*
You can see how this is all applicable to D&D....
4th ed is a HELL of a lot more tactical than prior editions, thankfully.