The Real Problem with "Dynamic Ques" Isn't Matchmaking Imbalance
While I doubt the matchmaking for Solo players will allow climbing opportunity equal to a 4-man premade, the main issue for me is that this new system would be a poor indicator of skill. At the very least, it would be quite ambiguous regarding its significance. A fairly weak player can just communicate well with his 4 other friends on Skype and climb while being quite subpar. On the other hand, if this same player is placed in a different group where this isn't possible, he may be several tiers worse. Likewise, a group of players might just develop some sort of cheese strategy (a creative level 1 invade etc.) that they just repeat over and over to climb. Essentially, it's much easier to get carried or simply to develop some formulaic strategy that you can get the whole team to follow. Thus, one could easily climb without being able to adapt well to changing game circumstances or even being decent in one's favorite roles.
Solo Que requires being able to work together with many different kinds of people and in several roles. Moreover, it requires constant adaptation since you don't get to develop some grand strategy before the game or communicate in great depth. Every game is different and you generally need to be pretty proficient in your role to climb consistently. This usually means above average mechanics for the champions played and good understanding of matchups.
These styles and the abilities a high ranking requires in each are quite different. One's ranking in the new system no longer assumes certain skills based on various ranking tiers. It cheapens the meaning of a higher ranking because it can mean too many things. Let's say that one has a geography and history class but they are graded together. What would a grade of B mean? It could be a student with an A in history and C in geography or vice versa. Perhaps it is a student with a B understanding of each subject. You just don't know. That's why subjects aren't graded together. The measurement would no longer make sense as an indicator of understanding.
jungle
mid
top
bot, and never lose a single teamfight as 5 man premade