Hm... that is strange, at that point I would have to say it would have to be the desyncing on the client and server side of things. There are occasional bugs still lurking about that can sometimes pop up. If you can, I'd advise putting up a post in the in-game bugs section of the thread if this still continues throughout normal gameplay. Sorry I can't be of more help on this one. I hope you'll find your answers soon though. From my knowledge, aside from BLM's health to mana conversion there isn't a skill in the archer/bard arsenal that drains one's own hp.