-All of them seem to fit their class fine except for the zombie pigman.
-The witch surprised me. Not what I was expecting at all (in a good way).
-The zombie pigman doesn't match his role here, but there's nothing else I can think of, so I won't deduct any points.
-There are no FPS arms.
-Ghast throws dirt blocks.
This is a great mod. But I would suggest that you just remove the FPS arms from the boomer, the hunter, and the tank if possible. I would also suggest that you change the ghast a little bit. You should make the ghast throw fireballs, rather then dirt blocks.
Over all I highly recommend this mod to anyone who likes minecraft.