Battlemaster was never touted as underpowered or boring to play before Tasha's and power creep reared its ugly head.
Battlemaster did a few extra dice of damage per short rest.
The way to make it not suck was to turn those extra dice of damage into extra hits and extra chances to hit.
Precision, Riposte, Brace.
Now your dice stretch out over a few more rounds, and each use is about twice as strong.
Then, have 1 additional use of dice that you pull out when you crit. The rider doesn't matter, so make it trip or disarm (both of which are situationally useful).
The traditional BM, who uses their abilities to do damage and do tricks? It is pretty lackluster in my experience; you barely notice the effects of the subclass abilities.
Champion is not boring, it is simple. There's a difference.
No, Champion is boring. You can make a non-boring champion that remains simple.
These are the baseline, certainly, but that doesn't mean everything that follows has to be "moar power", in fact, I would argue it is determental to the game when it is. Things need to be new, but balance with what IS already in the game.
So the Champion's level 3 feature is poor design. It gets more powerful at higher levels, and in fact is most powerful when used as a 3 level dip by a level 17 character who has another source of advantage.
On a level 3 fighter, having a 19-20 crit range causes barely noticeable change in play.
A level 3 subclass feature should have maximum impact on a level 3 character of that class, not minimal.
And deciding not to take a subclass shouldn't feel exactly the same as taking a subclass. That is what the champion feels like; you didn't take a subclass.
The 2024 one is slightly better; remarkable athlete moves down to level 3, and feels like it does something.
But I still think it needs something, like "when you take a second wind, you can make a melee weapon attack".
I find this statement laughable, but hey think what you want.
Oh, sure, and over powered to a crazy degree when actually played.
I'm playing a Rune Knight (Barbarian 8/RK 4) right now.
I'm not using the Stone rune (I'm using the Cloud rune). Btw, the Stone rune effect is a joke in that it makes the creature Stoned.
Creatures worth using a 1/SR ability on tend to have legendary resists. Anything else, the best condition is dead. The fire shackles have a decent chance to do nothing on a front-line opponent. If they do do something and it isn't a legendary foe, well, if there is focus fire the creature you hit is dead within the round anyhow?
It does let you hit a creature then decide to leave them alone and go after someone else.
The stoned rune produces a weaker effect than Hold Person, a 2nd level spell, most of the time. It does, however, not eat an action or concentration. Hold Person causes auto-crits
and scales, with higher level spells targetting more creatures.
Compare a level 5 Rune Knight to a level 5 Warlock.
L5 RK: Two attacks, ~12 damage each, melee. 16 AC (no-stealth penalty heavy armor, not super-expensive)
2 single-target disables that don't require actions. (cloud and fire rune)
Action surge, second wind.
L5 Warlock: Two attacks, 9.5 damage each (13 if you use Hex), ranged. 14 AC (studded) Two casts of hold person (2 targets each) or similar spells.
Pact boon, subclass, 1 free invocation (the other was agonizing blast)
Suppose Hexblade. Then damage (with hex) hits 16 per tap (x2), get 19-20 crit range, and a 9 point heal when they are defeated. Plus medium armor.
Like, I'm not seeing the huge gap.
The Hill option? That is just a 1/SR rage. And it uses the same bonus action as getting big the RK wants to use. In a 3 round fight, it sucks to take 2 rounds to "scale up".
If you consider this "average", your style seems OP to me and way above what I like to play (which is fine for you, of course!). Do you even use anything prior to Tasha's still or did you just jump on board the 2024 boat as soon as you could? I would think it has the power you probably prefer? I know I will never play 2024 material, for example, so that should give you a good concept of what I consider overkill to enjoying the game.
But yeah, I challenge you to show how
any of the subclasses in 2014 from PHB or Xanathar's offers as much candy as the Rune Knight does.
I mean, Diviner? The Totem Barbarian (resist all but psychic)?
A subclass should actually do something. Two characters, both the same class and a different subclass, should feel different to play with.
2014 Champion really feels like "you forgot to write in your subclass" in actual play.
By level 20, the funny thing is that the Champions features start kicking in. The extra crit range matters more with higher end weapons and more attacks, for example. If you graph a naive "I hit more often to do more damage" BM against a Champion, the BM damage is way higher ... until late T3, when the Champion catches up.
At low levels, the difference between the Champion and the subclass-less fighter is smaller than the difference between the Champion and the BM, and the only class feature the Champion gets is damage.
So, if you think the Champion is a well designed subclass, I'm not sure a subclass that does anything at all at the table will pass your standards of "not OP".
Note that the 2014 BM outdamages the RK still - the RK has lots more utility than it has raw damage output.