I remember when the Titans was a thing, a squad of unrelated characters faction wise who dominated arena for a while. The squad consisted of Rebels (CLS, Han, R2), a Jedi(GK), an imperial (GAT) and the occasional clone(Rex) who would replace r2 in some matchups.
Ever since then we basically haven't had any decent hybrid squads that could compete in arena with the likes of RJT, NS, Bastila, Palpatine and eventually Traya and Revan. This is consequence of overpowered leadership abilities that provide way too many bonuses for same faction characters. This also creates a small problem which is that it doesn't allow for some characters to thrive when paired with random characters.
Some of the examples are Rey, Revan, Traya, Bossk, ect. When you take these amazing characters and try to plug and play they end up failing miserably. It's almost sad that you can't use Revan with success without other Jedi. Or that you can't use Traya uless she's accompanied by Sion and Nihilus, or how you have to have BB8 present with Rey.
I find those things to be somewhat disappointing and I'm looking forward to the next decent hybrid squad that could stand it's ground against the likes of Revan.