It's more than likely 1 really strong player with Tendo Pain and maxed buffs.

Generally, Tendo team is: MB (+80 chakra with lightning armor/bloodthisty) +nin/tai to lightning ninjas
Tendo slot 2, Asuma WB(+nin/tai max hp), and:

Hashirama (+nin) Tobirama (+tai) Shurado (+tai) Chikoshodo (+nin) Konan (+nin/tai), Darui/Danzo(barrier for lightning) all buff Tendo from any formation.

My Tendo at around 27k bp can generally wipe the board if I can collect all the buffs, just try to minimize the combo chance of the other players turn 1 ninjas. I tend to get around 3min clear time with a few combos going off. The real problem is the lag of the battle taking up 1min+ becuse of ppl with slow computers or the network.