So how exactly will the Mentor System not be abused?

[Vivi_Bushido]

I'm actually a bit curious if something like, the new players need to vote if you were helpful or not at the end of the dungeon and you get a reward based on that would be abused in some way. I can see a tank or a healer holding a group hostage, but at the same time even if you say "I'll give you my vote" to get the party going you could easily just... not vote for them.

You mean like player commendations where 80% of the community leave instances without commending anyone because their standards are too high despite it not killing them to give to at least one person?