My initial concerns are:
1. Commander's strike - this is already really in the right party under current rules and even better with your rules IMO.
2. Riposte - any time I'm missed I get a reaction I can attack the enemy with. This is amazing!
3. Parry is even more impressive now too - reaction for flat damage reaction on an attack - no more variableness. Very nice!
4. Menacing attack - chance to cause fear every single turn (can be used from range). This is way too strong.
5. Feighnting attack and a rogue multiclass produces a reliable way to always gain advantage.
1. At will is always better IMO, but otherwise you are giving up your attack
and bonus action and your ally is giving up their reaction, just so they can make an attack on your turn. Now, with things like SA working once per turn, this could be abused... but with 4 superiority dice per short rest already, given the "normal" encounter rate it seems to already be there. I could remove the Battle Master bonus for the ally to offset the power a bit.
2. Sure, but since you can only use one maneuver per
round, you can't use any of them on your turn... at least not until 15th level.
3. The variableness would more likely produce a higher result than the flat bonus. And again, it means you aren't using any other maneuvers on your turn. In that sense, it is no better than Uncanny Dodge.
4. Fear which only lasts for one round provided you hit and they fail a save. Until I playtest it some, I am okay with that.
5. Sure, but denies you Cunning Action, TWF attacks, etc. It is a trade-off.
But what about the ones which already required a bonus action? Like Feinting Attack?
They still require it. There was no way to make it cost more.
How do you think wizard fans would feel if you reduced all their spells to be equal to cantrips, but useable at-will?
Personally I wouldn't care since this isn't about wizards and I am not making it for wizard fans. If I battle master fan joined our group, I would of course take his thoughts into consideration and work with him on something playable. If he wanted to play the BM RAW, that would be fine. This is because I don't like the resource management aspect but want a comparable at-will version.
I feel like this under-powers the Battlemaster quite a bit. That is how I feel anyway with the shift to bonus actions powering everything and the decrease to the additional bonus they receive.
Commander's, Feinting, & Rally all use BA currently.
Sure they can these features every round if they wanted to with this shift, that is nice.
It means you can't be a two weapon fighter Battle Master. Not nearly as effectively anyway as you're having to decide between a maneuver OR an attack every round instead of being able to do both.
You have to decide between Second Wind and these maneuvers as well instead of being able to do both.
Ok, but having the ability to use them every round doesn't off-set some of the power loss? It makes using bonus actions for other things more of a choice of course, but I see that as a good thing personally.
If I could think of another mechanic other than bonus actions which would still allow at-will use, but have
some cost, I would certainly consider it.
Do you allow more than one bonus action or reaction in a round in your games? Because otherwise, the 15th level feature is practically worthless.
Also, as a general side note, I feel it'd be more elegant to have the battle master bonus be equal to proficiency modifier. (Actually, I'd prefer a lot more things be equal to proficiency modifier or a multiple thereof- like rage damage or the various half your level extra damage racial features.)
Oh, thanks for pointing that out. I meant once you use your bonus action for one maneuver, you can still do another. Alternatively, I would also allow the combination of bonus action
and reaction to fuel two different maneuvers. I'll have to give that some thought.
Proficiency bonus would work as well, but it makes the Battle Master bonus too good at higher levels, nearly equal to the average superiority dice. To off-set at-will I wanted to make the bonus a bit lower.