Here is the end result.
I found him actually a very effective tank. His health is similar to that of a Rogue tank, his protection value was in between a Fighters and a Rogues, his evasion was much higher than a typical Fighters, and his resistances were very good. Overall he tanked like a champ. I used Shock the entire time, only getting some in fire for the resistance.
There were some advantages and disadvantages. The major advantage I found using a mage tank is that I was able to have two Missile Weapon Rogues in the back shooting volley upon volley. This is because I didn't need a torch. His damage was very high in the early part of the game, but it slowly scaled off a bit later on. I could have gone for Fireball and Zhandul's Orb for higher end game damage but I liked the casting speed with the Orb of Radiance, it synergized very well with the attack speed of the rest of my group. His energy pool didn't suffer considering he was only casting a basic spell.
The largest disadvantage if it is one. Is that you need all the Tomes of Wisdom in my opinion, and of course the Tome of Health. Mage tanks definitely aren't for someone on their first go.
There are definitely a lot of different options to how you chose to build a mage tank. You could definitely try to balance damage and durability, I went for as durable as possible.
Here is a picture of him around level 6, just to show he was very tanky even during the early-mid parts of the dungeon.