Best build - Get Haste, MAX Defensive Spell Mastery, have at least 1 point in Devastate. Keep buffs up at all times. The rest of the points you may spend as you please (ie: adventurer, dual wield, martial weapons, shadow armor, etc.) depending on what weapons you like to use, but the idea of this build is to move around the maps as fast as possible while dealing the most damage to everything. This build will let you beat the main story in quite a short time once you get the Haste spell. I suggest that you use another defensive spell for your other spell slot and then use Identify Item spell along with the Teleport spell.
Stats per level: 3 Strength for every 2 Defense
Gear: pure DPS, raw DPS no procs/drains etc > armor base > balanced resistances.