another suggestion to make it more playable for temas on bent:
Make a kind of "additiona-attempt-points". For every killed Boss the team gets 1 point. When a team dies and has such a point, they have a next chance in this level.
So for example a team could beat Boss 1-2, fail first attempt in Lv 3 and win in the second and has now 3 trials for Lv 4...
what do you think?