Pet buffs certainly work on charmed pets, but their haste is capped and they'll only melee twice a round. Depending on what you're charming, they'll usually hit harder and have more hps than your normal pet.
I'd just experiment if I were you. With FD, mezes, and slows to undead, you can get into pretty hairy situations and still come out alive. Plus that will be more exciting than your usual grind. As far as zones go, I'd check out HoM, Cata, Freeport (undead monks might be good) and Eldenals (undead courtyard area). Maybe some necros can add further to your question, but those areas would be places I'd check out if I played a necro.
