Oh you're in diamond 4

@Tperodactyl 

That kind of ranking system you mentioned (diamond going only vs other diamonds) would lead to an almost continuous flow (as long as people keep playing ranked) of players getting to Master hardstuck at 10.000 RP. Theoretically, look at it this way:

If Diamonds only fought other Diamonds, the "best" Diamonds would  progress the fastest through the division and reach Master first. These players are now removed from the Diamond matchmaking and at the same time, the same exact thing is happening in Platinum and the "best" Platinum player reaches Diamond4 and are now in the Diamond-only lobbies, many of them being "the worst" Diamonds. Now when the "best" Diamond players are out of the matchmaking, the "better", i.e  slightly worse than "best", Diamonds are now the "best" in the Diamond matchmaking queue and will eventually reach Master and the loop  will theoretically go on and on until pretty much everyone can reach master.

This phenomena is even a thing with the current matchmaking system; you can CLEARLY feel the difference in average skill level at Diamond as the split goes on. So to put some limit to this, I think its very necessary that Diamonds have to start fighting the big boys in Master/pred IF they want to start grind towards Master. I played to master some splits ago and its not like the majority of a Diamond 4 lobby are Masters or preds.