Palpatine lead should be better, focus down on R2. Other enemies do minimal harm to your team. R2's burning is all they got, really.
I saw a thread that these event foes are all set to level 1 abilities, so Han solo can't stun except on his first turn, Leia doesn't hit much, R2 doesn't stun as much etc.
Nevertheless, R2's burning does the damage of 15% of the max health every turn. So it all comes down to how fast can you take the droid down.
With Zader lead, you need to stack ton of dot. Slow, but it will die eventually.
With Palpatine lead, you might stick some more debuff on them and keep R2 out of stealth, and tankers from taunting. With some crit damage mods (36% or 66%) on attackers, he does die quick without the benefit of infinite dot. My g9 186% crit damage TFP, for example, critted for 30k and removed R2 quick enough.