How about a tank that dual wields shields.
Like for aoe agro spell he could bang the shields together like a taunt similar to flash.
And for aoe damage he uses all his might to smash them together and create a shockwave.
Combo rotations involved attacking with one shield and then the other and for finish combo stroke with both shields at once.
And as an equivelant to holmgang hallowed ground etc he could have a buff where he reflects 100% of all incoming damage back to attackers for 5 seconds.
Could also give him some kind of bar similar to red mage which is based on left and right shield attacks.