Well in my guild we usually have a tanking-rotation, meaning that everyone gets to tank.
For instance I MT Ignis, another guy MT XT-002 and so on.
However we usually prefer using druids (we got 2 ferals) on slow and hard hitting bosses. Take Ignis (pre-nerf, since he hits like a pussy now) and Steelbreaker. Both of these can(or could) easily hit for 30k+ on a single hit.