Warlocks (in PvE) are currently one of the best DPS you can get (If not even the best). They also have great, chainable CC with the glyph of fear nowadays. Affliction was VERY VERY VERY VERY (can't emphasize this enough) broken some patches ago, warlocks we're getting some 400k drain life ticks and the like.
Blood DKs are (from my healer perspective) the best tanks at the moment. Great cooldowns, invaluable self-heal if the shit hits the fan. Can't tell much about PvP, haven't queued for BGs in the beta yet, and TolBarad battles at the moment are everything but PvP.