I estimate 35% losses taking Garth down (yeah I made that up). It would be the most devastating mutiny in the history of Starfleet. He would most likely anticipate the whole mutiny and be ready for them. It might even take a joint op between multiple CREWS. Only when his supporters see how far gone he is would they turn and join the mutiny and defeat him.
Ok, my hopes are dangerously high. If Garth is not captain, someone must promise to make this into a fan film. Written by Trek BBS. :-D
Garth should have been the villain of STID....as either the Khan role with powers, or as the Starfleet veteran going crazy.