I've started doing random heroics again now that I realize I may need to get some side-grade ArPen gear. I got assigned to an Oculus group. The tank insta-dropped. We signed up again and waited. And waited. Well, after 5 minutes I whipped out my turtle. Interestingly enough I was perusing the pet talents and noticed that it was borked. Badly.
It appears that if you go from 51pt BM to something non-51pt BM all your pets talent trees are hosed. I didn't really have 36 talent points. I had 16 to spend, but I couldn't spend them on any of the talents I wanted.
The solution is to head to your pet trainer and re-talent all your pets while you are in your new MM spec. Yes, all your pets. Re-spec'ng pets doesn't appear to cost anything.