One of my peeves about downed characters is that enemies will continue attacking someone who's down in order to kill them. Then, of course, it's annoying that anytime you get a chance to "help" someone, they are immediately downed before their turn so you wasted a turn for nothing.
I'm also hating concentration spells. Anytime I've cased a concentration spell with Shadowheart, she's immediately lost it before the party could benefit from it because she'll get targeted right away and fail a check.