If you pop battlemaster trinket and call your pet (or resurrect your pet), you pet's health will scale from your buffed health and it won't drop until any of you dies, you change items on yourself or change instance.
I only found this working with Inherited Mark of Tyranny with BM hunter. I speculate that it works for warlocks and other pet users.
Tried using search function but haven't found anything similar, maybe did a poor work, sorry in advance if this is a repost.