As it is you get 1-5 XP i think for completing a quest. Also i have noticed that doing elites you get very little bonus in XP.

I would suggest to be more in line with the hugely growing XP requirements and to be more in-line with other MMO RPGs
Let's break quests down into different types and then show the XP suggestion
Boss kill quests = (Player level * 5) ranging from 5-125x in this expansion
Non-boss, 1 time only quests = (Player level * 3) ranging from 3-75 in this expansion
Daily Quests = (Player level * 1) rangng from 1-25 in this expansion.

Similar with Elite mobs and bosses. with the crazy time it takes to kill mobs and bosses maybe it could be more worth our time.
Make elites give 3-5x more xp than those same mobs do in regular mode.

just a suggestion. I think doing some random dailies etc could help break up the monotony of doing W4 to try and reach max level (or W3 when max was level 16).