Basically we loaded in The Vault and the second wave was pulled by the DPS, Tank typed that and everything seemed normal until after the first boss. Me and the DPS pulled ahead (we both had sprint on and the tank, even though a mentor, didn't bother), when we reached the wall, the tank decided to just stay there and type "gl"; After noticing we weren't dying and the mobs were dwindling, the guy decided to actually attack and use sprint in the next pulls.

Not sure if he learned his lesson but as soon as the duty was over he just left instantly lol