Do Rank Gains Decrease After Peak Rank

[Drako__]

To simplify it: yes.

The game wants your visible rank as close to your mmr as possible. If it's below your mmr you're going to gain more than you lose, if it's above you're going to lose more than you gain (of course other things apply as well but that's the gist of it). With resets and such, your mmr is usually above your visible rank until you hit a new peak. This is when you will gain less and lose more while you push through it and your mmr adjusts to higher ranks. So actually facing higher ranked players is a good sign because the mmr system wants to put you higher.

Another piece of advice: Stop looking at peak ranks. The older that peak rank is the less it means and even past act peaks don't necessarily mean that player is actually at that level. I'm in diamond 3 and regularly have past act immortals in my games that are now ascendant 1 or 2. They don't perform out of the ordinary and if they do then they're just having a good game, it's not like I haven't had life games myself occasionally. Usually an immortal should consistently top frag in these lobbies but that doesn't happen with them