Nah, that is way too abusable like someone said above. People could just sit in there for an hour and run the clock out for no reason. Yeah, you can kick but the other 2-7 people in there would still have to deal with their time being wasted.

Might be better to reward more completion points for harder things. So EX Primals and harder things maybe give 2 completion points toward the achieve. Still encourages mentors to help with harder things and doesn't have the drawback of intentional stalling.