Being at range does nothing when enemies come to you, and any workaround is just going to be messy.

Casting on the other hand could work, as long as most casts were shorter (ie. 1.5 seconds) and they have a way to make them instacast for movement. Though they would have to be based on Strength as opposed to using INT for obvious reasons.

For a tank using 2 shields, I just cannot imagine their attacks would be interesting. There is only so much you can do animation wise with a single shield, let alone 2. So I cannot see that happening.

A 2 handed hammer would be most likely, and if you combine that with a caster, you could have a tank that enhanced their hammer swings with magic to do their damage/apply defensives.