My rogue got jumped last night by a hunter. I was pickpocketing and beating on some of those weird half-demon types in NE Desolace, fairly close to Nijel's Point. He sent his pet in just as I was finishing off the first of my two-pull, but fortunately the hunter was 4-5 levels below me.
I pop sprint, try to close some distance, but he gets off a concussive shot and I don't have imp sprint, so the likelihood of my taking him down seems slim. In desperation, I pop vanish, knowing full well that his pet will break it almost as soon as it's up. But it didn't happen that way. A miracle happened--the pet de-agro'd. Went running back to the hunter. Vanish WORKED against a pet. Now with a couple mobs on him and me stealthed, the hunter decides to exit stage left. I gave chase, but couldn't risk coming out of stealth with so low health, so I quickly lost sight of him.
I dunno, I don't get to play my rogue as much as I'd like, so maybe I'm missing something here--but isn't this THE major complaint about Vanish? That it rarely if ever breaks pet agro?