I know for a fact that after some point, curing hunger does stop working. I think it works for a little while, but then stops. Then again, I never pulled out my pet and waited to see when it stopped attacking. I also noticed that when I came back to my computer and it was starved, I couldn't just feed him for him to fight again, but I had to completely re-equip my pet.
If you want to set up your AI to attack anything that hits you, that is one spot. To defend itself, that is another spot. If you put curing hunger in, that is your third spot. I don't have a Ruv, but I know that my jag, poly, kai, lingko, and zeppy only have 3 AI spots.
If you can come back and feed your pet whenever it is hungry, you can replace curing hunger and place defend itself in the first AI slot with a skill; then defend itself/you for the other 2 slots with attack. In this scenario, it will first use it's skill on whatever hits it, and whenever available when it is still being attacked. Defending you and the pet will also keep the pet attacking instead of just stopping its' battle.
I think this will work. Either way, we need more AI slots for p2 pets.