OOM window switching

I was running my 3 ele shamans today and noticed my main was running out of mana farming the monkeys outside Pearlfin Village while my two slaves showed a full bar. I switched to another and wala, the new main was empty and the previous empty main was showing a full bar. What is up with this? Is it a new bug from 5.2 with Isboxer window switching? I know it's not just showing my slaves as full when in fact they are empty too, because they would keep casting while my main is empty. The slaves lose no mana whatsoever, they can cast endlessly but the main goes out fast. This doesn't matter if I use lightning shield or water shield. Same results.

I too was bummed out when I tried running a bg for the first time in a week and thought man, I need to reboot my toons aren't following. I will just make up for it in world pvp by crushing all the cry bags with my 5 dks.