My pet's dont heal, at all, ever. I have pets with sprite, fairy, and unicorn, and on my level 35 ice, in ALL of the times of questing, my pet has healed ONE time. Why does this happen?
May casts on healing have been adjusted. Awhile ago MC Sprite was adjusted to no healing when you were full health - for some reason most of my pets took that as don't heal ever any more. A few months later MC Fairy Friend was adjusted because apparently having to much healing while in battle is a bad thing. There again most of my pets took this as meaning only heal 3-4 times in a time block of about 6 hours of battling. MC's on Unicorn and Healing Current seem to fall even further back in the food chain as they seem to cast rarely across my pets that have that talent.
You don't seem to be able to up your odds of MC by having more healing in one pet either. Across all my pets healing is rare but some more then others. Currently most to least for me are: Spritely, Fairy, Unicorn, Healing Current. I do not have any pets with the life bat healing so I can not say for that one.
It's pure luck. I find that my pets cast Spritely and Fairy at the same rates, Unicorn and Current are definitely lower. I haven't seen the supposed claim that pets no longer heal when full health, mine do it all the time. I tend to have the opposite problem, they like to spam heal me when I don't need it and totally ignore me when I DO. They also do better in full parties with other healing pets because there are more triggers and even self triggers. Every pet goes through seemingly indefinite "dry spells", but I find mine tend to step up again when around groups. It does make it more difficult to solo play.
Its all random happen stance. It wont happen all the time and the MC abilities have different triggers in battle. I have been in battle in WW and stuff with others and their pets heal constantly because the triggers are being hit each time in battle. Dont worry if it doesnt happen all the time. sometimes it does sometimes it doesnt. If you feel as though its a pet thing just hatch it again and see what happens.