Game Mechanics: Health bar not updating on mobs

[Sorn]

Something of a one-off bug that was resolved easily but thought I'd make a note of it here.

First saw griffin hanging out on the slopes, tried to grab it but got the 'you cannot see your target' messages even when right beneath the griffin. The griffin vanished, then another (or the same one?) showed up again in a slightly different area like it had just traveled on its usual path. Pulled that one, it promptly nuked me (something none of the others have done all day). Feared and dotted it to let it die slowly. Noticed when I was lowish on mana that for some reason the griffin was displaying 100% health even though we'd been at it for a good 7-8 minutes.

Screen Shot 2015-09-21 at 10.45.43 PM.jpg

Moregan showed up to look and saw the correct percentage. I fixed the display bug by targeting him and retargeting the griffin, but got a screenshot of the weirdness first.