In Warlords of Draenor, all of the stats have been squished and experience gain was no exception. Blizzard got rid of high numbers and values and lowered them instead. The latest beta build, increased the XP required to hit a certain level by 30%, for each level from 89 up to 99. At level 90, a quest yields approximately 15,000 experience while mob kills earn you 500 XP.
Updated experience requirements can be viewed in the table below: