I had a tank doing this during one of my 'hero' roulettes, just flat out ignoring our requests to move it, addressed them by their name, used sounds, even auto translated basic directions.. anything to get their attention and after awhile, .. I told the healer to let them die >.> and when he did, we pulled the turtle over to the smoke uty complete:

But if it's a mage and tank combo.. that'd be a lame troll indeed...