Necromancer's Intensive Mender frequently either heals less often than it should, or not at all.

wheem_ESO

Oftentimes, my Magicka Necromancer's Intensive Mender will simply float around on top of my character, and not actually cast any heals at all. This is despite me not being at full health, not LOSing the pet, and not having anyone else around "using up" the heals. In some instances, it will cast 1 or 2 heals per 8 second duration (instead of the 4 that it's supposed to), but I just completed a Battleground where 7 full duration Menders in a row resulted in a grand total of 0 heals. That's 56 seconds straight of my pet just floating around not doing anything at all, while my Stage-4 Vampire regenerated from ~65% hp to ~80% hp.