Animist gains XP after death if spores are still active.

[5n1perwo1f]

Animist class has an open exploit in which they will die, but continue to gain XP from kills that are targeted by their summoned Mushrooms. To replicate, lay down some mushrooms and have them pull in mobs. Once you have a set amount of mushrooms, allow a mob to kill you. During the release timer you will continue to earn XP for each kill by your mushrooms.

[OntheDOL]

I would say this is working as intended. Same goes for DoT's, I know i died alot on my cabalist at the goblins in Lyonesse but would still receive the XP if the goblins died after I had died and not released.

Now unless you are talking about the Animist's main pet? (which has no despawn timer) That pet should die with the Animist. The other pets last up to 2 minutes as far as i know.