My understanding is that the experience values have not changed, but rather, the amount of experience you receive is dictated by the difference between your level and the level of the dungeon. Therefore, because of the change, you will see more higher level dungeons, which give a smaller relative bonus. It's worth mentioning that these bonuses are balanced with the EXP you are expected to receive by running the dungeon. A level 32 dungeon gives you far more experience per kill than a level 15 dungeon, meaning that the lump sum experience reward at the end has been set to make them approximately equivalent.