I agree with Konrax with his sentiments there. It doesn't necessarily need to be an attack that does any major damage at all, more for the tactical anti-spam. If someone comes at your shield hitting constantly it could just be an attack to give you a breather, after all if someone has a 2h weapon in extremely close quaters and you have a shield you would almost certainly use it to push him backwards instead of just something to be hit non stop.
As to Dexxtaa, why not make it so that launching forward to knock them with the shield prevents you turning in either direction, so as a 2her if you have the range you could move to the side and slice as he is off balance? So basically it could be a weaker kick but with more protection at the front given that there is a massive shield there.
Again these are all just ideas, I have no idea how the would implement them. Talking about ideas doesn't hurt anyone though.
All the best,
Ben
EDIT: Just seen the idea about a timer for the sheild to prevent spam. That sounds pretty good, if your by combat and it takes like 10 seconds to regenerate then your not going to want to waste it. Smiting could be the anti-spam attack, breaking heavy spam of you shield to give you a quick break, more importantly it would give shielding a bigger role.