There are many players out there that are far better players from learning how to play before coming to MP. Why do so many have no inclination to join a clan?
I have never seen a player come from sp and be good right away at MP.

Agreed: what is weak, what is strong?
Its realative as to whos playing. If in a 4 on 4 .7 players are equal and one is weaker rest assured a good team will find that weakness.

4 individually weak players who work as a team will beat 4 starplayers that don't.
Isnt this what clans are about?

Again Im speaking of BAD players like those [cF]Adherbal was speaking of. In those cases the games over before it begins. I guy who takes all v0 units and no range units has pretty much condemned you to loose before the battle even starts.