Classes game is in need of?

[Wrot]

I was wondering if there was a shortage of any roles at the higher end of the game. Do raids get called for want of a healer, tank or slower? Is it difficult to get in a group as a damage class?

Short introduction, I loved raiding endgame as a necro from 98-2000 and I would like to get back. I've been raiding in WoW since release, but my guild has everything dead and there is nothing to do till next xpac. Sometimes we have to call a raid just because one or two healers didn't log in (end of the expansion/summer downtime). I was considering rolling one of the trinity classes if good players were extremely hard to find, or if the dps population was saturated.