Matchmaking should consider players individualy too. In my oppinion it has the same importance as alliance level and alliance trophy average.
For example if just one a player in alliance A has 4000 trophys and the strongest player in alliance B has 3500 trophys, alliance B players will not pass through a 4000 trophys player.
Maybe could be used tiers like the ones used on ninja event to rank players. In this way, If we got the same example, a perfect match for alliance A has just one player between 3850-4299 trophys (same tier), same trophys average and same level