just to add my 2cents. When I came back 6 months ago, I jumped from 5boxing to 7boxing. Limited by my computer. I tried 8, but it wasn't happening in TB.
I run, HPally, RShaman, Hpriest, and 4DK. Like many, in Cata I had 4Ele Shammys, I had the 4Ret+1DK, and some other various experiments. I love outdoor pvp. The past few months, I login, check the TB timer, note it, come back later. I do a handful of instances for mounts, and that's it until MOP.
To my point. I think you should consider 4healer, 6dps when 10boxing AV or Isle. You want to take on 30+, you need the heals for it. Adding 2 healers to my team, insane boost in TB. My dps is the same, I just outlast them all. I have easily taken on 3x my team in TB.
Areans, not so much lol. I am just average, I have been hovering 1500-1600s. I try not to take it to seriously, always for points/ gear.
I am have been kicking myself. I saw someone post their pvp video, think it was a 10boxer. He had like 4 druids healing his DKs. Looked sick. I don't think my Rshammy and Hpriest are the best choices, but I am going to make it work in MOP. I just don't want to level up or xfer another toon anymore.

Acid