I can beat all tiers past and present with maxed ep lead, rg, vader, g8 hk, and g8 ig. However the bonus tier appears to have a bug. The Elder is resurecting on the players turns instead of its turn. So you take a turn or two and a resurection happens each turn then the elder gets a turn and actually uses his skill to resurect. Ive even seen him resurect while stuned as well. After 4 tries i was able to beat the bonus by subbing g8 R2 for ig. But that is purely RNG luck.
Playing your skills right has always been a factor in this event, but that means bubkus when the end death squad all go first and hit for 70 to 80k dropping your team before your first move. All my toons sre 190 to 230 speed.