Realm - Crossrealm
Spell/Item/Mechanic - The MMR/rate system.
Date tested - 01/09/2015 ~~ 01/11/2015
Description - The rate gain until you reach ~~1500ish is very fast, going from 0 to 1000 as ~~48 rate per win and from there and on, most give you 18 rate per win and a minimal reduction in your rate per loss. This is because once you start, you have around 1500 mmr set as default, and as you lose/win you get more and more(1500 might not be the correct value for 5.4.8.), but it seems that in PandaWoW this value seems to have little to no alteration at all, specially because the rate gains at high ratings gets irregularly low(this is, taking in account that the enemy team that you won had the same rate as you), and a loss reduces your rate drastically(about -30 or higher).
How it should work - The MMR should increase properly with rate.
Comments - Unfortunately I'm not able to give that many details, specially because there aren't any solid/trustable/clear about how does the gains and losses works.
Priority - 10/10, this is the core of the competitive arenas.
Blizzard Thread
If you have any thought to add, please do it politely in the comments.
Also, thanks to Noneedholy for pointing and discussing this.