Why Light Side is the perfect decision for TB.

The problem is that any imbalance is only in your mind. For almost all content you can use mixed squads.

It sucks you can't use dark side characters in this particular Territory Battle, but eventually there will be one that uses dark side characters.

Liking the evil characters is all well and good and go ahead and farm them, but if you're ignoring over half the characters in the game because all you want are the evil ones, then that's on you.