Link to build:
The idea is using all Fire spells with the Burning Axe of Sankis, which boosts their damage by 25% on a perfect roll, and 2 piece Tal Rasha's for another 3%. Only 2 defensive skills are used- Slow Time / Time Warp (which is also a DPS boost) and Ice Armor Crystallize. The Axe makes it possible to drop Diamond Skin- it's proc is the Barbarian ability Ignore Pain that has a chance to trigger when you are hit and it has no internal cooldown.
I used both Meteor Shower and Molten Impact, but I prefer Shower with this build for wider range AOE because of the narrow focused effects of Fire Bolts and Mammoth Hydra. Mammoth Hydra can be recast immediately after it fires its trail to fire another one which stacks. You can use Mammoth Hydra and Meteor Shower for offscreen kills on low MP.
Arcane Dynamo boosts both Meteor and Hydra.
I had close to 1600 LOH and was getting by with Blood Magic for LS on MP7.