I farmed 80 AB marks before i turned 70, i did most of them in the 50-60 bracket and did so at level 59. It was the best thing i ever did. As much as i enjoy quad boxing AB, its usually 50/50 chance of winning and is totally dependant on your team mates. You could say this about most other BGs but for some reason i get a much higher win rate in AV / Eots.