So this has been annoying me for a while now.
These 'mini mobs' don't have the health bar appearing and you can't tell if they're tagged.
I've tried deleting the following folders:
Does anyone else have this?
How to fix it? etc.
"it isn't a bug, it's a feature"
I think those odd health bars are working as intended (but I don't like that too). The monster portrait color changes to a darker tone when someone else is tagging it as I remember!
Herald of the Titans
They have gray frame when untagged so it is not bug per se.
What I can say you is to advice Tiptac or some other tooltip addon, you will be able to see if mob is tagged or not by mouseover.