As it is now fates really is the only viable option. Some daily instance or a daily quest or two that grant significant exp would help the constant repetitive fate grind.
Also I believe dungeons should have some replayability at high levels for a couple reasons
A) keep ques flowing
B) helping low levels through dungeons and catching up
Need to remove several dungeons as many of the lower level ones are quite redundant, increase exp gain(duh) and perhaps item quality as well.
Increasing higher level players to return to lower level dungeons isn't really that hard there just needs to be some sort of incentive and significantly fewer dungeons. Perhaps a vanity currency for dyes, fashions, makeovers or housing.