I think there was less RNG in 5v5. If you lost one ship, no big deal. If you lose a ship in 3v3, your chances of losing go up a lot more.
Right now Ackbar is 95% of the fleet meta, I'd bet that the other 5% is probably from newer shards that don't have the Ackbar Falcon fleets to deal with, at least as much as the rest of us do. We don't have the numbers, but in my fleet arena it was always a mix between Tarkin and Thrawn.
I can still get #1 daily, but some days RNG just decides I'm not gonna win. I've had a couple days where I lost 3-4 of my daily fleet battles because of RNG hitting me. If my Falcon survives first attack, I'll win.
At the least in regular arena I can find the occasional Darth Revan to attack. Regular arena battles are much worse and take too long. I doubt that'll change the next time Darth Revan arrives and I can get him since most of the rest of my arena will get him the second time too.
I deal with it and do the battles everyday because there's a big chunk of crystals available for being #1. It'd be nice to get another option that can be beaten, not just another option that you have to spend money for and you can't beat with anything else.