I'm biased since my original character is a feral druid that tanked everything from Stockades up. That said, in my opinion a feral tank is a legitimate but not ideal option for five boxing. It's easy mode with crowd control from three mages, but I wouldn't be so keen to try and hold aggro in the face some of the larger dungeon pulls in a CC-lite group for the very reason Kadaan and Toned mentioned.

On balance, bear tanking is a fun alternative and keeps you on your toes a little more.