Diminshing quest xp formula?

[Xuluman]

What is it in vanilla? I found somewhere on wowwiki that if char level <= quest level + 5 you get 100% xp. Well I completed a green quest which fulfilled this condition. A duskwood quest that involves killing mobs definitely should yield more than 500xp. So this formula is probably wrong. But then, what is it?

[Heldunder]

leveling takes a lot longer in vanilla.

[Robotron]

Welcome to Vanilla.