I do think this pet is running the ragged edge of unbalancing (which I one of the reasons I work rage the way I do). I make sure the wolverine isn't too bright, and closely enforce the number of commands it knows, per the Handle Animal skill. I also reduced its HD so that it is appropriate to the party level.
Yes, animal companions can be a pain, and the druid can be a little over-powered, if abused. Keep them in line by:
- Playing them like animals. Remember low INT, frightened/skittish about things that are unfamiliar, and they don't necessarily do exactly what they're told.
- Enfoce the handle animal skill. The wolf might know the command "Attack", but WHO it attacks may not always be certain, or obvious. Most animal companions aren't awakened, so they'll only have a few commands down reliably.
- Animals put their interests above the druids, generally. The wolverine in question runs from strange magical beasts, constructs, and other things that are completely unfamiliar.
- Animals aren't likely to go into strange places of their own accord (like some strange dungeon settings).
- Large wild animals result in the druid being treated cautiously, or with mistrust, by the surrounding populace. Makes getting a room at the inn hard with a wolverine following you around, trying to eat the wizard's cat, growling at the patrons, etc.