70-74 and 80-84 Arena

My cousin and I started doing some 2s at level 70 for fun. I was told that you can still do arena at 71-74 and receive rating, so I leveled to 71. We did some 2s and went 15-0, my cousin received rating, but I didn't (he was still 70 at the time). We didn't know what was happening so he leveled because we thought we had to be the same level or something; he lost his rating and stopped receiving rating.

At that point we decided to level to 80 and do some 2s. We are both 80 at the moment and receiving rating. However, most of the time we face players that are 84 and pretty much one shot us. I have talked to some of the players we faced that were level 84 and they were receiving rating.

I'm a bit stumped here. We don't want to level and stop receiving rating. We've tried playing with xp on and off, still nothing.

Any ideas/thoughts?