Just a little request for the Devs to try something small that might be interesting.
Next update, pick 4 or 5 quests that are seldom run and are at a wide spread of levels.
Possible examples:
3 - The Sacred Helm
6 - The Troglodytes' Get
11 - Raiding the Vulkoorim
16 - Servants of the Overlord
21 - The Lost Thread.
Then, just for a period of 2-3 weeks, dramatically increase the XP on each of them so that they are on par with the top XP quests or even a fraction above, and publicise this.
Compare the player reaction to this to a 'standard' 10% or 20% XP event. I think it will go down well.