I've been killing Succubi this week-end and it's too much a mess to kill them without peace. I used only my vanguard horse, and without peace it was non-stop Greater Heal. That wasn't possible for me as I don't have a 100% LRC suit, so I decided to peace them. And I noticed that when it was still peace when my pet gave the last hit, I gained no Honor. But if the Succubus was "awake", I would gain Honor.
In all honesty, if you can avoid peace, it's better. It's sometimes tricky to have it unpeaced for the last hit, and when the Succubus "wakes up", the pet gets its rear kicked while the Succubus chains heals. So if you find a good mob that allows you to stay near your pet to vet, it's better.