Altmer is best currently. Don't neglect regen, also stamina. And you need an idea how to actually kills people, be able to create bursts.

Burst is imperative. You can spam overload light attack all day and some opponents will just shrug at you.

Imo the best way to burst (without magicka det) is Velacious curse and Mage's Wrath and Crystal Frag (or Overload said moves on bar) degeneration helps as well.

The idea is to do enough damage to get thru shields etc before they can heal it back. Timing when a curse goes off with a frag and Proccing a wrath can be all that is needed. Remember you have a 4 sec window to proc wrath, meaning if your opponent is cocky you can wrath, then curse, then a normal move (seeing as the normal move is the only real dmg so far they may not set up defenses) then curse, then a procced frag and a proc from wrath all occurs in one seconds. Massive damage.

Or if im in a group I like to spam wrath, with so many players hittin the opponent I almost always only have enough time to get the proc off