Help me out...

As your main focus is on GAC, I'll rate the teams in GAC order.

1. Cere/Malicos
2.  Darth Revan/Imperial Troopers (Are very closely matched.  Imp troopers are probably a little better.  However, the Darth Revan death mark can be clutch.  There's a clear difference when you get Malgus though).
3. Seppy droids
4. JKR
5.  Tarkin/Darkside clones.  (I'm not sure there that viable outside of 3v3).

Note though, outside of GAC,  Cere/Malicos is probably the worst team on that list, bar the Tarkin one.  I'd also say that the Cere/Malicos team is the least useful too.  Not used for any events or needed for any unlocks.  No ship viability either.  

NineTails426 wrote:

If there are other squads that are fun to use,

Darkside Mandos are a lot of fun.  Also, a great clean up team.  Bad Batch,  Cere UFUs, Palp/SK 'can' be fun, but also stressful at times.   For me, Raddus/Rogue 1 is distinctly unfun.  I hate using that team, very stressful.  I find the teams where you're waiting for the stars to align are....distinctly unfun.

NineTails426 wrote:

no, I will not be including Galactic Legends.

Not thinking about GLs (or meta fleet ships, even better) is a mistake.  You're swapping temporary form in GAC for suffering later down the road.  You need to aim big with your unlocks.  I understand your reasoning, I reasoned the same.  However, you have to do it and the sooner you get started, the sooner you become someone to really be reckoned with.