Solo queue should be just that - SOLO
Two man and three man groups just destroy solo queue.
If they are on your team, they go into their own little two man world and pretend the other three players don't exist. It's impossible to get them to help the team because they only help each other and leave everyone else for dead.
Regardless if they are on your team or the other, they could have huge advantages if they are friends who can chat live without wasting time typing, or if they just know each other's play style.
Two and three man groups should have their own completely separate queue. Mixing them in with the solo queue is just wrong and it makes the game extremely unfun for the other players. Not to mention that if there is any negative attitude, they will gang up and blame the more vulnerable solo player.