I did this once as a warlock in a group without a hunter. No one actually blamed me and was heaping abuse on everyone but me until I spoke up.

First time I'd ever run a dungeon as a warlock or any class with a pet, so it was... odd. Last time I did it, though. I've since learned to watch my pets.

Somewhat related, as a 'lock I had my voidwalker out while leveling, queue came up and almost immediately upon entering the instance I had half the group yell at me to dismiss my voidwalker. Like, I get it, but the screen had barely finished loading.