This post will stray a lil bit from the original intent of the topic but since OP has begun to join the discussion in this direction, I suppose it'd be all right.
Ever since I posted earlier, a few people have pmed me in game to point out the fact that there are plenty of people in 71-80 bracket to start arena. Something like this "There are 12-13 people (in the bracket) online and around 20-30 that i know of." Their conclusion is that quantity is not the problem, it's incentive to pvp.
While incentive to pvp is indeed a concern, I'd say the number of players is the bigger problem. Sure, 12-13 are greater than the 10 needed to start HF. But not all people pvp, and of the people that pvp, they might be doing something else at a particular moment. When they're ready to pvp, they might be ready at different time. If this is confusing, I will use a simple illustration: "For 1 player to voluntarily queue up arena without special incentive (dailies etc), you need around 3 RANDOM players of that brackets online" So in essence, you need 30 random people of that bracket online for HF to start. 3 is a charitable number, I'd say the real number is 4 or 5.
Some cool incentives can be added for arena to start but the real problem won't go away. At some points, the drive from those incentives will be exhausted and arena will die again. Dynamism is the essence around which pvp is built, and it can only be attained with a larger pool of players.