I think that while the steps Blizzard has taken to combat people who enter Alterac Valley and then sit in the cave and go Away From Keyboard are a start, there's still a ways to go to fully solve that problem. The central issue is that a person who is AFK in battle either ends up with a gain in honor, or at worst, they stay level. There is no actual penalty for being AFK.
Sure, there is an opportunity cost involved. The AFKer doesn't gain as much honor as she could. But most likely she is doing something else, a non-WoW activity such as watching TV or surfing the net, that would prevent her from actively participating. The potential scenarios are:
1. Watch TV, don't have WoW running.
2. Watch TV, sit AFK in Alterac Valley.
In the worst case, the rewards for the second scenario are equal to the rewards for the first scenario. So there is essentially no reason not to AFK while watching TV if you can.
It all comes back to Coriel's First Law of Skill:
If the metric used to measure skill cannot decrease, you are not measuring skill, but time.
Honor cannot decrease. Thus it measures time, and people will come up with ways to make it look like they are putting in the time.
The AFK Debuff needs teeth to be useful. It needs to have an actual honor penalty in order to make scenario 1 preferrable to scenario 2. Unfortunately, this might open the doors to griefing as sub-groups in AV try and declare other people AFK when they are not. An example might be a group of 70s trying to declare any non-70 in AV as AFK, in order to force them out.