I've noticed that while trying to level my avatar, once i got up to 15k xp killing npc in highvale, my xp began to drop. Is this to prevent farming (hey, I need the gold to explore leveling other skills)? Also, I have two xp bars. One is something like "pooled dev". Difference?
Whenever you use a skill, a certain portion of your pooled experience is siphoned off and applied to that particular skill. The higher the skill level, the more experience that must be siphoned off to increase it. So, if your pooled experience starts to drop, it means you are no longer making sufficient experience from each kill to satisfy your skill leveling requirements, and you need to locate some higher level opponents. The other bar is the "Producer Experience", used when skilling up Crafting skills.
Also, despite the use-based skills system, "adventurer level" is still an important stat for PvE combat. (It can be seen at the top of the V window.) It raises more slowly as it increases, and as you get more skilled, you should move into areas with stronger monsters. You can look at the name colors on monsters to get an idea of how strong they are. I'm not sure I remember the colors right yet, but yellow = too low (you will likely lose XP from your pool to feed your skills), blue = about right, and I think red = RUN! (Even that isn't necessarily true, I fought the fire elemental yesterday, name in red, to unlock advanced fire skills, and it barely damaged me as I slowly chipped away at its HP. But that was as much player skill as it was skill points.)
I used to be in the camp that the PAE system sucked and we were all going to be miserable once we run out. I feel dumb now, as Ive totally figured this out, and pretty much continuously have a solid pool of PAE. Bottom line: you cant level everything simultaneously forever, or for very long. Focus on a small set of skills at a time, then level the others. You cant become a master architect, kung fu master, painter, hockey player, assassin, linguist, chef, dog trainer, astrophysicist, and day trader all at the same time.