I encounted this issue, and was wondering if anyone else has experienced it. I have a darkness spec bd, so I'm working with fossil mystics. Loving them. However, I've noticed that they randomly stop attacking/casting. Once they do they will no longer take any actions. They just stand there looking dumb. So, I release, resummon, and move on. I never played a bd on live. I assume this isn't normal behavior for this pet, but I'm sure there are people here that would know far better than I. So, is this normal?

Ofc it's not normal. This bug can happen to any caster AI in the game right now. That's the reason why I decided to skip BGs with my necro because it happens so often in pvp. In most fights your pet doesn't cast or attack. While you are using all your power they follow you doing nothing. Release and resummon is the only solution which is not possible for pvp.