It is working as intended. You just have to realize that there's an over abundance of mentors out there. So if it can't find a new player, it'll throw you in something random to help que times for people waiting. Another thing is, just because people have multiple 60s doesn't be they don't need help. Contrary to popular belief, Mentors aren't limited to just helping first timers. It's entirely possible that someone in that party could've used some kind of advice somewhere in the dungeon, such as pointers for their rotation. Need to keep the world free of Ice Mages ya know.