Of course, The experience earned of each Hostile NPC probably doesn't have any definite numbers attached to them.
But In my opinion, although I haven't been very active on the beta, I played It actively around the first 2 or so weeks and due to personal reasons I haven't played much as they were slowly increasing the Max level in the beta. But I think due to Blizzard's current plans for their dungeons with CC etc dungeons and mob tagging will be near impossible to achieve you a realm first level 85, so it think getting the early quests done at release and beating the rush will achieve level 85 the quickest.
So what do you guys think will be the most effective way to level in cataclysm if you had your goals set on achieving your realms first level 85 class be it warlock, paladin W/e.
Theories, any Math you may have is welcome .