You are not getting outplayed when the enemy composition just has a lot shorter cooldowns or a lot more cooldowns to press. Then you are basically only getting outcomped. RMX was here no difference to Ret+Arms right now, just with the difference that you can move you character and not being forced into afk for 50% of the times because of spamable cc.
You could have seen historical ladder data on xunamate back until WoD season 3. Not sure if there is any other site currently that provides historical arena data for you to check.
Well, if the comp is op how is that different? RMP was broken in countless seasons, so nerfing rogue and mage would have solved that problem.
People always said that you might punish other comps with that, but to be fair 90% of rogues and mages were playing rmp, so that would have been fine.
But history also have shown us, that rogue always found a comp that was broken. If it wasn’t rmp, it was thug, rpx, rlx, rogue+ele and so on. It’s the stun based class design of rogue that is broken.