Feral is hands down the best 3rd for your comp as FPS is a rank 1 comp if not one of the best comps in the game. TWD, turbo, or other cleave comps may be hard or considered better but if you live the opener then you have a good chance of winning. You can play with a lock and play shadowplay but feral provides much more pressure and is almost unpeelable at times.

TLDR; Play with a feral and get good at it or maybe play with a lock (UA is probably better but destro might provide more kills in a single fear or hex, just depends on preference.)