Just some notes in case someone else wants to try...
I got 2 PBBs in about 90 minutes, but keeping both cleared was a little much. The spawn time was closer to 6 minutes flat (360 seconds vs 400).
Keeping both cleared would have been fine, even if a little tight except that if I let them live long enough they would eventually charm my pet so I tended to nuke them down too much (I was uncomfortable with the fear kiting path). If a pet did get charmed, it blew the cycle completely as I had to FD and resummon pet (350 mana) and my INT was only 161 (hey, I was camping PBBs, alright!?!
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It didn't occur to me until after that I might have been able to break charm with Cancel Magic, but Evil Eye charm doesn't work the same as PC charm so I'm not sure if it will work. I'll try that tonight because I want to get a couple more for my baby milk elf mage.