Ackbar challenge is pretty hard, yeah. I got it done when I had 5 ships at 4*, but I had Wiggs at g10. But I think you can clear it with good rng, and definitely will get it done if you continue to work on the toons.
Now the Tier V... even the only light whale in my shard has Ackbar at 5*, so I don't even try... my best ships are dark side, so it needs a while until I have enough ship power on light side. At least I got Wedge to g11 and Ahsoka is close to g11 too, Biggs at g10 and JC at g9.4 are ok too, but it's tough to build enough light side ships and toons, I am gearing Resistance Pilot and Poe because I have them 7* already.