This idea sounds interesting. Do you still keep action surge as a "per encounter" ability?
Well, it's still a work-in-progress, but here's what I do now for Action Surge... likely I'll be tinkering more...
Replace 2nd level Action Surge with
Warrior's Gift, which provides 3 options, one of which is the PHB Action Surge. The other two options are...
Against the Horde
Starting at 2nd level, you can sacrifice one of your attacks on your turn to make a number of additional attacks equal to your proficiency bonus against only CR 1/2 or less creatures (e.g. hobgoblins). Each of these attacks must be made against a different opponent. You may only sacrifice one attack to use Against the Horde on your turn.
Starting at 17th level, you can use Against the Horde versus creatures of CR 2 or less (e.g. ogres).
Stalwart Defender
Starting at 2nd level, your opportunity attacks don't require a reaction, though you can only make one opportunity attack against a given creature in a round. The maximum number of opportunity attacks you can make in a round is equal to your proficiency bonus. Additionally, while you are not incapacitated, you can make an opportunity attack against a creature that moves more than 5 feet while within your reach.
Starting at 17th level you have advantage on your opportunity attacks.
[SBLOCK=Detailed Comparison] Action Surge (the baseline for comparison)
Action Surge (baseline)
I assumed Action Surge is used on average 3 / day, due to the DMG assumptions of 2 short rests/adventuring day consisting of roughly 6 encounters. Technically, the DMG says 6-8 encounters, but I low-balled it for easier maths and because it seemed safer to err on the lower end.
At 2nd-level, Action Surge grants 1 attacks. Used thrice/day, that's +3 attacks/day. OR +0.5 attacks/encounter.
At 5th-level, Action Surge grants 2 attacks. Used thrice/day, that's +6 attacks/day. OR +1 attack/encounter.
At 11th-level, Action Surge grants 3 attacks. Used thrice/day, that's +9 attacks/day. OR +1.5 attacks/encounter.
At 17th-level, Action Surge grants 3 attacks. Used six times/day (thanks to the feature improving), that's +18 attacks/day. OR +3 attacks/encounter.
And at 20th-level, Action Surge grants 4 attacks. Used six times/day, that +24 attacks/day. OR +4 attacks/encounter.
Next, I thought about my rough target for Against the Horde. Because it's circumstantial according to the challenge faced (only working against CR 1/2 or less creatures, at 17th+ level CR 2 or less creatures), it should be a bit more potent than Action Surge...maybe granting something like 1.75x or 2x the number of attacks/encounter. That's just my ballpark value eye-balling it. However, there are two important things I'm bearing in mind:
CR 1/2 monsters are common at lower level. Therefore Against the Horde shouldn't be too far ahead of Action Surge at lower levels.
CR 1/2 monsters, even CR 2 monsters, may becoming increasingly rare at higher levels. Therefore Against the Horde should significantly increase in power compared to Action Surge at higher levels.
Against the Horde
For Against the Horde, I assumed that in a 6 encounter adventuring day about half the encounters offer use of Against the Horde. I further assumed that AtH could be used fully in the first round of an applicable encounter, and used half as effectively in the second round…due to monster attrition. The decreasing appearance of lower-level monsters at higher-level is very roughly offset by the 17th-level increase in CR that Against the Horde can target. I also assumed that despite increasing monster group size, the fighter's increased # of attacks and the party's ability to handle large mobs increases in step with the number of monsters.
So, for 2nd level, here's the calculations I made for Against the Horde
There are 18 combat rounds in 1 adventuring day
normally 18 attacks at 2nd-level
but 3 of those rounds
have +1 attack thanks to AtH (i.e. sacrifice 1 attack to gain 2 attacks vs. weaker monsters)
and another 3 of the rounds
have +0.5 attacks thanks to AtH
= for a total of +4.5 attacks / day
So the values for Against the Horde (AtH) look like...
At 2nd-level, AtH grants +4.5 attacks/day. OR 0.75 attacks/encounter.
At 5th-level, AtH grants +9 attacks/day. OR 1.5 attacks/encounter.
At 11th-level, AtH grants +13.5 attacks/day. OR 2.25 attacks/encounter.
At 17th-level, AtH grants +22.5 attacks/day. OR 3.75 attacks/encounter.
And at 20th-level, AtH grants +22.5 attacks/day. OR 3.75 attacks/encounter.
This "feels" about right to me, even if I'm making some small mistakes with my assumptions (e.g. maybe I should have assumed two full rounds use of Against the Horde at 17th-level due to targeting CR 2 or less and the generally larger numbers of low-CR monsters required to challenge high-level parties). But overall, until the very highest levels, it puts Against the Horde just ahead of Action Surge...the price being that Against the Horde's usefulness hinges on just how frequently weaker monsters appear in a given adventure.
Stalwart Defender
What this does is gives the fighter more battlefield control but requires that the player strategize the best place to position his or her character, and encourages teamwork. Trying to move past the fighter becomes a losing proposition. This preserves the coolness of the Sentinel feat, which more closely models the 4e fighter's "attack my buddy? well I'll attack you!” But how to even begin balancing this?
How often are opportunity attacks coming up in an "average session"? Well, with the PHB rules at most 1/round, because each creature gets 1 Reaction per round. So the question is how often will the warrior get to go above this 1/round in an adventuring day? And roughly how many additional attacks do they get to make?
Same assumptions as above: Adventuring day with 6 encounters, each encounter lasts 3 rounds.
Maybe half of those encounters the warrior is facing fights with enough monsters and enough movement to get use out of Stalwart Defender? So in those 3 encounters where Stalwart Defender comes up, it's probably reasonable to say the 2nd-level warrior gets at least 1 extra attack somewhere in each encounter. I estimated lower than Stalwart Defender's full potential because at lower levels it's really hard/rare to face large numbers of monsters. That gives me a starting point at least.
At 5th-level, I'm assuming the warrior gets at least 2 extra attacks somewhere in each of those encounters. Not the full 3 because that starts to make the battlefield cramped, and scenarios where you have a huge team of monsters rushing past the fighter within his reach seem kind of rare. Again, super tough call to make. These are egregious assumptions, but some kind of balance is better than none.
That's the assumed pattern I'm using then, that Stalwart Defender allows PROF BONUS -1 extra attacks at least one time during the encounter (or possibly in aggregate, it depends on the encounter). So at 11th-level that becomes 3 attacks, and at 17th-level and 20th-level that becomes 5 attacks. (*)
Accounting for the 17th-level advantage to opp. attacks (*) is a bit tricky, but basically advantage is measured as being worth +25% chance of success on average (yes, it varies by target number). That's the value the core books give it, so I'm following suit. The way I can interpret that is to give the number of extra attacks/day (or attacks/encounter) granted at 17th-level and 20th-level a x1.25 modifier, representing more of those attacks landing.
So the values for Stalwart Defender (SD) look like...
At 2nd-level, SD grants +3 attacks/day. OR 0.5 attacks/encounter.
At 5th-level, SD grants +6 attacks/day. OR 1 attack/encounter.
At 11th-level, SD grants +9 attacks/day. OR 1.5 attacks/encounter.
*At 17th-level, SD grants +18.75 attacks/day. OR 3.125 attacks/encounter.
*And at 20th-level, SD grants +18.75 attacks/day. OR 3.125 attacks/encounter.
With those assumptions, it looks like Stalwart Defender is very comparable to Action Surge, perhaps falling slightly behind at extremely high levels toward the end of a PC's adventuring career. Which seems about right, because Stalwart Defender is something with a trigger that the player can orchestrate meeting (unlike Against the Horde) but it does require some strategic thinking and good positioning (unlike Action Surge, which itself is limited by short rests).
It is possible, however, with a different set of assumptions, that Stalwart Defender could seem less or more powerful on paper. I suspect this is one that would need to be playtested to really get a definitive answer.[/SBLOCK]
I still think I would prefer "at will" abilities, but perhaps giving action surges instead of straight multiple attacks over the Fighter levels and giving them the option of another normal attack or a "feat/stunt" (which would need to be pretty powerful) when using an action surge would be cool (?)
Agreed. A couple thoughts.
First, some players are like you and I, liking "at will" abilities which feel more like the old school fighters, while others like "powerz"; the fighter should endeavor to accommodate both styles. Doing that while avoiding bloating the class to too many pages...that's a trick I'm still figuring out.
Second, for "stunts", I'd actually look at giving the fighter alternate uses for Extra Attack. Sacrifice an Extra Attack to boost damage and do a special stunt. For example...
[SECTION]
Aimed Shot: When you use the Attack action to attack a target, you can take an aimed shot to ignore half-cover and reduce three-quarters cover to being only as effective as half-cover for purposes of your aimed shot. If the target has no cover you instead gain a +1 bonus to hit. You can only take one aimed shot per round, but in order to use it against the same target again you must spend one round observing the target and making no attacks.
Improved Aimed Shot: In place of two attacks, you make a shot ignoring half and three-quarters cover entirely (or gain a +2 bonus to hit), and your attack deals two extra weapon dice of damage on a hit.
Master Aimed Shot: In place of three attacks, you make a shot ignoring half and three-quarters cover (or gain a +3 bonus to hit), ignore any disadvantage on your attack roll, and your attack deals three extra weapon dice of damage on a hit.
[/SECTION]
[SBLOCK=Quick Maths (edited)]When a 5th level fighter (with 16 Dex and a longbow, and Archery fighting style) uses Extra Attack, he makes 2 attacks with a +8 attack bonus, dealing 7.5 (1d8+3) damage with each attack, for a total of 15 damage if both attacks hit. Against AC 15 (which the DMG tells us is normal for a CR 5 monster), he hits on a roll of 7+, which is a 70% chance to hit. His DPR = (0.7 * 7.5) + (0.7 * 7.5) =
10.5.
If he uses Improved Aimed Shot, he makes just one attack, but his attack bonus becomes +10, and he deals 16.5 (3d8+3) damage. Against AC 15 (which the DMG tells us is normal for a CR 5 monster), he hits on a roll of 5+, which is a 80% chance to hit. His DPR = (0.8 * 16.5) =
13.2.
When an 11th level fighter (with 18 Dex and a longbow, and Archery fighting style) uses Extra Attack, he makes 3 attacks with a +9 attack bonus, dealing 8.5 (1d8+4) damage with each attack, for a total of 25.5 damage if all attacks hit. Against AC 17 (which the DMG tells us is normal for a CR 11 monster), he hits on a roll of 8+, which is a 65% chance to hit. His DPR = (0.65 * 8.5) + (0.65 * 8.5) + (0.65 * 8.5) =
16.575.
If he uses Improved Aimed Shot, he first makes his special shot with attack bonus +11, dealing 17.5 (3d8+4) damage. He then makes a third regular shot (as above). For a total of 25 damage. Against AC 17 (which the DMG tells us is normal for a CR 11 monster), he hits with his Improved Aimed Shot on a roll of 6+, which is a 75% chance to hit, whereas he hits with his regular shot on a roll of 8+, which is a 65% chance to hit. His DPR = (0.75 * 17.5) + (0.65 * 8.5) =
18.65.
If he uses Master Aimed Shot, he makes just one attack, but his attack bonus becomes +12, and he deals 23 (4d8+5) damage. Against AC 17 (which the DMG tells us is normal for a CR 11 monster), he hits on a roll of 5+, which is a 80% chance to hit. His DPR = (0.8 * 23) =
18.4.[/SBLOCK]
