As a Mentor, I know any duty have a timer. When and if I enter Mentor roulette, I know I can enter either a sweet dream of a fast run, or a living hell lasting all the time the duty allows. I know it. I accept it.

Whoever makes shortcuts and ditch the duty because he pugged something different than the speed-run they wanted, needs have Mentor status permanently revoked. I'd give maybe a warning or two before this kind of punishment, because everyone can have a bad day and we are humans.