I currently aim for 5* since i lack Trooper Shards and only have Pilot+Phasma geared/leveld enough, but Kylo and Officer progress much faster so if needed i should have them at 7* and i also hold back gear etc to adjust. My Problem is, i will not buy the FO pack if i only need 1 Toon. So unless CG split it up to get a single char, i will not have BB88 at 7* which really hurts because i invested my first year in droids and have all of them at 7* and more or less only use them at HAAT... I tried an Arena comeback with R2, but it doesnt work and i need a top20 team which is able to get 1-3 till payout.
BB8 is no CLS, Thrawn, Nihilus etc. so it is a very specific investment (he is made more for Droids, but even resistance is not a factor for arena etc.) which means only a small amount of players will a) buy and b) have all 5 FO (the only one in the game!) characters ready - because FO is also not "broken" enough, even with a bunch of zetas(!). Its nice that FO players get a gift, but it is a shame that droid lovers maybe dont get this good designed robot for their collection.
I have 1,5 zeta ready for BB8 but i will wait for the first test runs - if he is good enough to bring droids back (at arena) i will invest with gear/abilities etc. - if not i will only unlock him.
As i mentioned above, the team is more or less set in stone, HK, R2, B88 forms a solid support trio for the robots, than you need more damage: IG88/IG86/ (GG/IG100) and support/tanks (B2/K2/Chopper).
All configs need to adress currenty top team problems, which comes down to CLS-Counters (CLS/R2/Han), which are super deadly for the old HP/Prot canons like IG86/88 even more if AI will use AI (also a problem for B2!). Stupid Zarris/GK or even other top speed control characters like R2/Thrawn that interrupt with Steahlt/Fracture and high speed.
Unless someone find a good (AI friendly) combination to fire of BB8 special before the team is dead, i think K2 is needed as a tank to soak up (counter)damage, he spams offense down which is good and offers daze(!) with a solid hard hitting punch too.
R2s AI will use Smokescreen first so the first AOE Move from every droid should be safe, but keep in mind that Raid-Han will more or less Oneshot IG88 at the start of the battle...
I think Grievous (while still without a rework...) can be a solid sleeper IF you have him at G12 too, he gains a huge HP upgrade at G12 AND +50% Max HP for a full droid team, which means over 45k without Mods and Protection. His basic is still a very hard hitting and unavoidable (foresight spam Kenobi) and uncounterable (CLS/Thrawn). His AoE with healing immunity is also important against Zarris. So for a super small amount of droid players a maxed Grievous might be one of the best damage dealers in the current meta that is also able to take some hits - but most will not have him or will not invest THAT gear into him before a rework.