Premade groups in the DF queue in general can be a pain even if they are not trolling they will often gang up on the extra person they picked up if something goes wrong even if it wasn't their fault. The most irritating examples of trolling as a premade was back in CT because it's so easy to purposely cause a wipe you'd get a whole alliance of people from the same server who just joined to troll and you couldn't kick any of them.