I find most of the mage damage to be situational, 1 trick pony.
Arcane warrior build, requires tremendous investments in certain skill lines to make it worth while. Yet it's easily crushed by simple "dispell" spell.
AoE, is good, provided you can keep the foes there, and your team mates out, which's not always guaranteed. It'll also be another 60 seconds before you can cast the same spell.
There's also the problem with long cast time, plus most of the best spells are actually combination spells, it takes a while to set them up, and by that time it you might have missed the opportunity.
So I'd imagine the real Mage, single-target DPS is actually pretty low compared to melee. It's just that the AI being stupid (not going after the mage first, not stepping around AoE, or using Anti-Magic skill, and always crowding together) is what's making Mage powerful.
If this were a PvP game, I imagine the rogue would own just about any class, mage including.