So, i ran a couple of builds on the testserver, and i couldnt find any bugs so far. Stacking works properly as far as i could tell.
That said, when i made a 18 bard, 10 CL, 10 BS, 2 SD build to check out if everything works out with semi-persistent bonuses i came across a unrelated matter:
Snowflake Wardance has some serious issues. With the build above i was able to get some 3 AB from it at 30 and some 4 post 17 levels of bard, but according to the description it accounts for bard PRCs (which it doesnt), it also fired its fatigue thing off preeety randomly, sometimes after i rested and didnt activate the ability. And it didnt last nearly as long as it should have, with some 30~ base perform i barley got to 10 or so rounds.
edit: ugh, after realizing that i forgot to equip a charisma item, i am up to a 6 AB bonus and the duration works out fine again, im a dunce. (though according to the description the AB bonus should still be higher, i suspect there is something wrong with accounting casterlevels for practiced caster and bladedancer, or something)