Well, I don't really know what others think about this but I don't recommend to have 1 or 2 high level girls with low level girls in the same team. I think it's better to have less powerful girls with almost the same power. The team wil be more efficient. At least it's what I have noticed on this event with teams of 2 5* and 6* ~lvl60 (evolved, max affection) and some random unevolved low level 5* and 4* added just for speed.