For anything but 1-vs-1, individual skill gets smeared into the non-enemy (ally for team games, or everyone for a free-for-all) average.
Remember that cooperation isn't an individual skill (unless the meta is complete, I guess); it relies on knowing your specific partners.
And besides ... it's perfectly normal for a task-oriented group to have people at a variety of skill levels. If anything, homogeneity is what's strange. This does change what interesting interactions happen, but by no means prevents them.