So, maybe if I pin my thoughts down by typing them up, they will quit spinning around. (did I miss any directions there?)
There was a phrase in Asheron's Call I particularly hated: "If you ain't dyin', you ain't tryin'" Essentially it meant that, if you weren't killing things that had a high probability of killing YOU (that is, several levels above you), you weren't actually making squat for XP. Relatively speaking, anyway. I didn't much like dying, so I wasn't "tryin'" a great deal of the time.
In WoW, there seems very little incentive to kill things above your level. From what I can see you get about 2.5% more xp per level, but it takes rather more than 2.5% more TIME to kill them, so you get LESS xp per hour killing things above your level, then at your level... or maybe even a touch below your level. Unless there's a quest reward involved, it's just not worth it, except for bragging rights. Speaking of which, my level 27 Undead Priest managed to kill Sharptalon (level 31) on the second try. She likely could have done it on the first try, but a wolf spawned in during the fight and two was too much. Heh - that make me two for two doing Ashenvale's Great Hunt backwards. ;) Sharptalon (31) then Shadumbra (28) THEN Ursagous (25). I rather expect that's the way most people end up doing it, since Sharptalon is closest to Splintertree Post, Shadumbra is a just a bit farther and to the west and Ursagous is WAY the heck to the southwest.
You know, I still don't feel like sleeping. :(
Edit: Something to think about: the xp curve in AC was so steep, that spending a certain amount of time running back from dying didn't lower your xp per hour below what you would get steadily fighting things that DIDN'T kill you. It's scary, really.