If niten is still good enough to use instead of most other styles, then it certainly doesn’t need a buff.
Krav maga is good, but I’m not sure if I’d pick it over niten. It has rapid strike and downing strike (just 1 turn), stun on crit and break grab and a 20% boost to cut/pierce damage, a miniscule bonus to damage from strength and arm/leg blocks.
Compare to niten’s big passive boost to damage, extra blocks (won’t help against hulks, but…), big perception-based bonus to dodge (this one will), flowing water (a negative, but still boosts damage), downing on hit, stun on crit and rapid strike + stun after dodge.
Against hulks, I’d rather use niten, or maybe get a first strike with brawling (for downing) and then switch to niten.
Muay thai might be better, though. It has a 1 turn stun on crit, 1 turn stun on hit and full damage rapid strike with 1 turn stun on hit. Also arm/leg blocks and strength scaling, but those are minor compared to that full damage rapid strike with stun on regular hit. Seriously, full damage rapid strike with stun on regular hit - looks like an oversight to me.
As for the stat scaling: krav maga’s is insignificant (0.15 of strength - at 40 strength, it’s just 6 damage), muay’s is mediocre (0.5, but flat -5 to that, so you need 10 str to break even and need hydraulic muscles for it to really matter), while niten’s is actually good (1.1 bash+1.1 cut/pierce per point of perception, cutting works with cudgel too). 1 point of perception with niten is almost 5 times as good as 1 point of strength for muay.
But yes, aikido, karate, judo, capoeira, zui quan and animal based ones are underwhelming. Brawling is actually quite good, especially considering that it’s free, due to its defensive capabilities (downing and counter).