Just a note, it is very hard to tell if the system is matching players of the same skill level or not.
Yes, a Gold 2 player and a Silver 3 player will be, on average, of vastly different skill levels.
That being said, people's actual ELO/MMR is not visible to anyone anymore.
Positional ranks also vastly complicate things (Plat in one role and game knowledge, is in high silver due to not knowing the matchups of a new lane)
It is possible for 2 players of two vastly different divisions and tiers to in fact be of the same MMR.
Or Riot could be screwing around w/ matches to get more rage-playing or to keep people from their minimum-satisfactory-rank.
Hard to tell, the system is incredibly opaque.