BRD isn't really that good, especially after the demo shout nerf. I'm a little surprised you're having issues with mages in it, but it was a train wreck for my warrior group initially, so much so that I had to go to sunken temple where I was able to actually pound out the upper ring with the 6 bosses (I didn't do the bosses), until level 55 at around 40-45k an hour.

I went back to BRD at 55, and I was able to do the prison/arena and the Bael'Gar area with my 4 warriors "ok". It wasn't as fast as ST. Since your DPS is coming from mages, your issue really must be your tank, and mage efficiency drops way off if you're not doing bigger pulls with the way that arcane explosion is, and at 52-53, you're simply not going to be able to aoe grind that area of the prison beyond 3-4 elite mobs at a time, and that isn't going to lend itself to much efficiency for mage aoe imo.

Vipeax is different because he didn't use a tank, he finessed it with 4 mages which probably gave him the wiggle room on his aoe dps to kill stuff fast enough, in large enough groups, to stay efficient. I don't know if 3 mages can do what he did with a warrior slotting in that 4th spot, that's a pretty significant chunk of damage lost.

My advice might be to go check out ST for a couple of levels. I was clearing the upper loop in about 13-15 minutes, doing 40-45k an hour with reset, which was literally double what I could manage in BRD initially. I might not be the same for you due to mana vs rage, but, it's worth a try. I'm talking about the undread troll warriors, corpse eaters, and witch doctors, with the little imps. Packs of 4-6 or 7 mobs, with 2-4 elites.