Yes & yes. You are probably doing something wrong & sub does have problems on raid fights
A few anecdotal things I've learned is that timing is very important with this spec, likely more so than any other in current game. Your abilities need to be used with consideration for combo points, current energy, shadow dance charges, symbols of death & potential movement & your talent selection will impact this quite a bit as well.
I'm likely switching to assassin this week. The upcoming buffs to sub aren't going to make the rotation on raid fights more enjoyable, although it will raise your damage.