That was always my biggest gripe with the matchmaking of old. Teams had a certain average ELO, and the matchmaking would usually put teams together who combined, have a similar ELO. In reality what happened was that one team got a hard carrying player, while the rest of his/her team were underwhelming players. Whereas the enemy team wouldn't have one hard carry, but the average ELO of all players would be closer together, meaning that 6 players in the enemy team had a noticeably higher ELO than my 5 teammates, while I have a noticeably higher ELO than the 6 enemies. And thus the game basically expected you to "win alone", and overcompensate for the lack of skill the others had. Something that tanks W/L ratios, if YOU (a general you, not you in particular) are the one expected to carry the others. I don't want to say that I preferred that way of getting matchmade, but at least it didn't lag half as much...