The token system has been proven to work just fine in some other MMOs (such as The Secret World), but only if the dungeons are designed in a manner that makes the token farming grind actually fun and challenging. I’m not going to go into an entire explanation of the Nightmare-mode dungeon progression in TSW or the way that “Black Bullion” drops are awarded and converted to epic gear progression pieces in TSW; that’s for you to research if interested.
But I can definitively say that the system itself was never a bone of contention or player griping in TSW. It actually works very well and is a great incentive. GW2’s general system and length of grinding required is actually very comparable to TSW’s.
What’s different between the two games is that grinding these GW2 dungeons over and over is simply not fun because the encounter mechanics are totally, completely, utterly senseless.
Actually the very problem that the OP mentioned has happened in TSW. People only want experienced players with full clears under their belts and certain gear in their nightmare groups. Everyone just tries to clear dungeons as quickly as possible to get their black bullions.