Seen it a few times although none recently to report .... typically High level shaman's with a melee (monk or rogue) Shaman pulls with slow and then roots standing closer than the melee, the melee then moves or starts meleeing the mob until dead. This combo needs the last amount of input, as the shaman need not even do anything once the mob is slowed / rooted.
I think most infamously was the one that Famas caught on stream
https://www.youtube.com/watch?v=NfvADznhTQA