In my opinion, the best route to go is to dump EVERYTHING into Magic. Willpower is a useless stat for mages since Lyrium potions are dirt cheap (some three to five gold for ninety nine Lesser Lyrium Potions).
Spells to get:
Mage - Arcane Shield
Arcane Warrior - Combat Magic, Aura of Might, Shimmering Shield, Fade Shroud
Blood Mage - Blood Magic, Blood Sacrifice, Blood Wound
Creation - Heal, Glyph of Paralysis, Glyph of Warding
Entropy - Weakness, Paralyze, Miasma, (Mass Paralyze)
Primal - Rock Armor, (An offensive tree of your choice, I like the fire one as towards the end of the game, Flaming Weapons adds about fifteen damage. Cone of Cold is also a great crowd control spell, so you may want to consider it.)
Spirit - Mind Blast, Force Field, Telekinetic Weapons, Crushing Prison, (Walking Bomb, Death Siphon, Virulent Walking Bomb, Animate Dead - The bomb spells seem to be good AOE spells and Death Siphon could possibly help recover as much health as a Lesser Health Poultice, which is enough, given the fact that you are near invulnerable. The main point of this is to get the Animate Dead spell, which would tank for you while you fling spells, of course then, you should also get Spell Might, which is three talent points, so it's something to consider. I would only use this if I were to solo though. Maybe. I don't have a lot of experience with this tree, so it's all theory.)
Generally you have two ways of playing: walk around with all your sustained skills on and act as a tank or play as a normal mage. The beauty of Arcane Warrior is in the sustained spells: you can activate them when you have no mana. So, you can walk onto the battle field, fire off some spells, drain your mana supply, activate all of your sustained spells and auto-attack everything to death. The noly reason for more Willpower is to sustain more spells.
The Arcane Warrior is the best tank you can have. Even the High Dragon barely did any damage to me, so I was able to solo him.
Anyway, for equipment, this is what I used towards the end of the game:
Head: First Enchanter's Cowl
Weapon: Spellweaver OR Blood-Gorged Amulet
Belt: Anduril's Coil
Off-Hand: The Rose's Thorn OR Fade Wall
Boots: Imperial Weavers
Body: Reaper's Vestments
Gloves: Wade's Superior Dragonbone Plate Gloves
This is the best setup for a nice balance between tanking and casting, with a nice 40% dodge bonus.
[font="Times New Roman"]“The world breaks every one and afterward many are strong at the broken places. But those that will not break it kills. It kills the very good and the very gentle and the very brave impartially.”[/font]