On average WW is low middle of the pack. If played very well it can be much higher than raidbots shows. The top 5% push WW into the #3 spot in 25man Heroic. It depends on a lot, strategy, gear, skill, etc.
If you're talking about choosing a class this late in the expansion, you can honestly play whatever you want. Class balance is fine enough that even the worst DPS specs in the game are still viable. Playing something OP like a Rogue or Warlock would make things easier, but anything is doable with pretty much any comp if you're not pushing the final bosses of the tier on heroic.