I'm not sure how well ret can do anything right now, they're busy having their faces nerfed in. Probably still good for this, though.

Warlocks are supposedly not as durable as they used to be, I have no clue, haven't checked. But they can certainly handle multiple targets - if usually in a chain rather than all-at-once mode.

It doesn't matter much until you hit, say, level 40 content...the mage might be fast especially for the start, if you can play it well. But there's a reason paladins tend to get used for this. Even nerfed, I bet their mana issues are nowhere near that of a mage that is blowing AoE nonstop. Add to that plate instead of cloth and very minimal pushback issues.