Not that they could be abused just that the gamepad dosen't have enough buttons.
We'll only have 6 abilities on our action bars.
For ESO a current gen console controller will have more than enough buttons.
OP, their is software you can use that will make a controller work with an MMO. If the game doesn't directly support the use of a controller can still use one if you set it up right. I used my x360 controller for PvP in WoW for a while, it worked out nicely.