Fates are fine the way they are, aside from the amount of EXP, which a adjustment is in the works.

I'm sure you know how the system works? Bronze, silver, and gold you do enough work in a fate, you'll get Gold. If its a boss fate players usually don't run off, It also doesn't hurt anyone for players to run off to the next fate, unless you're at a boss fate and the tank leaves and it resets (seen this many times).

With the amount of people doing fates its actually a good thing people leave. That gives other players a chance to get gold (solo players, people who can't put an AoE on the ground, etc). So no, Fate system does not need to be reworked.