In GW Lando did his AoE 4 times in a row yesterday before I retreated. I was trying to focus on Palpatine first, and Shoretrooper slowed that down. I got it in the end, but that doesn't seem right that he is capable of that. And, we all know after that the damage is crazy from the second one on.
I run a droid squad in arena and my most disliked are these.
Wiggs - Prevents me from using AoE as I can't crit Biggs. The triple attack does insane damage and has a short cooldown. Even my B2 crits fairly often without any crit chance mods. With over 2/3rds still using this combo in my arena shard in top 50 (began in July, or maybe August 2016), I do get tired of seeing them. My success does seem to be very RNG dependent. If B2 or JE assist 86 then it can severely hinder me, and if I crit Biggs when I use B2 to remove taunts then that's rough too.
Palpatine - He always seems to stun 3 or 4 of my characters when controlled by AI. I always focus on him first when I can to kill him before he can do this.
Daka - Simply because she seems to res a lot when the AI controls her. She instant ressed Palpatine 3 times in a row on me yesterday till I retreated. Chance of that is 10% cubed, which is 0.1% I think... Fortunately, with retreat I can experiment till the RNG is more in my favor, and I like using her in GW for the same reason.
Lando - For what I said above. Unless Palpatine is there I always focus on him first. If anything I think they should lower his AoE, and increase his basic attack damage a bit, and not allow him to use his AoE 2 times or more in a row unless they lower the damage output to a suitable level to compensate. He also seems to be fairly tanky for a damage dealer, although he doesn't have otherm eans to protect himself.
New characters - I don't have much experience with them yet as not many people in my arena shard use them, but from what I have seen they are quite a step up in capability from older characters, and I would like to see them more in line with the others. Maybe, they are when other characters get zeta abilities, but that in itself is quite a step up to obtain. I don't mind them too much in GW though as they add a good challenge level, and beyond shoretrooper on the final 2 nodes, and occasionally Baze I don't see them much. Running B2 the taunt at the start of the battle isn't as difficult to deal with, though when I run other teams it isn't the same story. General Kenobi I have only run into a few times in GW, and he is pretty insane, though I don't have as much issue with him as I almost never see him, and he is a reward for heroic tank raid, which is quite an achievement in itself.
This isn't meant to be complaining about them per-se but I do offer some suggestions for some of them. Every team deserves to have counters and Droids have their fair share of teams they overpower, although hardly anyone use them, which I consider a balance issue. For example, my droids roll over almost any team without counters, particularly Jedi squads without much of the counter characters.