when buffed with buff of characters under lvl 85, battle roar don't even give you the heal it gives. i can understand he won't give you an another increase of hp of 10% but the 20% max hp heal is not to discuss, it should be working.
it's totally normal that you don't take the heal. taking the heal full buff it's a feature you take in some private servers. the fact is that the buff is giving all effect or none. if you are full buff , it gives none logically
is it so ? since i've played on off during interlude and didn't had the possibility to pay, my memories might be wrong.
i'm pretty sure it works like i said. never saw battle roar healing someone full buff except on some private servers.
there is one iss buff which is overriding the effect of battle roar. i don't remind which one but since the battle roar wouldn't apply under this buff then the heal won't work.
pipe organ melody (hp/mp/cp) also don't work with prophet buff improved condition (+hp/mp) and if your skill is lvl 5 and you have 6lvl hp bless/body of avatar skill also not work. (not 100% sure for last part, need to test).
despite what anxxi wrote, you can heal with this skill even if you've already it. but as svoloc said, the buff itself won't apply because already given by the pipe/condition (i.e : a more powerful one), and since the heal is linked to the buff, the fail of the buff leads to the fail of the heal. edit for anxxi : you could perfectly be full buffed (by having already the battle roar) and be healed by it if you reactivate the battle roar before its end.