Bah! I absolutely hate this class. It just doesn't look nearly as well designed as any of the PHB classes.
The sword shouldn't double as their implement. Why not model them after their divine counterpart, the Paladin, and have a sword enchantment that allows them to use it as an implement like the Holy Avenger or Pact Blade? That way you have a choice of using a melee weapon in one hand and an arcane implement (a wand!) in the other, or giving up your weapon special property to add the implement property to your weapon.
Aegis of Shielding is odd. It's arguably too powerful, it's not cool, and it's not as interesting a mechanic to work with as the Paladin and Fighter challenges. I'd design it as follows: When the marked target attacks someone other than you, you can teleport adjacent to them and make a melee basic attack.
If they really do get twice their int bonus to AC then that is completely broken for obvious reasons. Starting with a 20 and entering Demigod means you're pretty much impossible to hit on anything but a natural 20. You can buy whatever armor proficiencies you may or may not lack. Seriously, you're going to have an AC 9 points higher than a Paladin or Fighter in Plate armor; 11 points higher if they don't use a shield. Even if it IS just a straight +3 bonus I don't understand why it's 1 point higher than a heavy shield. Additionally, you may be able to use a shield in your main hand and just rely on something like Wizard or Cleric at-will powers to boost your AC even further.
Finally, and this is clearly a very subjective statement, I don't find most of the powers cool at all. People play Gish so they can hurl fireballs, teleport around, strike three enemies with a lightning bolt, etc and then mix it up in melee as well. The idea is that you have all these awesome single target and area of effect ranged magical attacks instead of the bow or throwing ax a normal fighter would carry, and then fight in melee the rest of the time.
This character doesn't do that, he just has a bunch of elemental effects for his sword. A warrior-mage casts spells.