I tend to agree with you, although you can't really blame the man! Plot realities called for some of the changes, like showing that the Forsaken are still human (I'll even give him a mulligan on this one since the myths of the Forsaken in the first 3 books made it necessary to make them seem practically omnipotent.

Here's a Moiraine-ism that I think highlights how loose the OP system was at the beginning:

EoTW
Listen to the Wind

"You have great potential, I think," Moiraine continued. "With training you might become even more powerful than Egwene, and I believe she can become one of the most powerful Aes Sedai we have seen in centuries."

Back in EoTW it seems even AS aren't all that sure how strong someone can become... obviously RJ made changes.

Personally I think the biggest shift we've seen in the OP strength area has been the difference between men and women. At one point RJ started telling and showing us how much stronger men were, but to your point it clearly dawned on him that it wouldn't work unless he toned it back or created some additional mitigating factors. Links seem a lot more potent, mixed circles seem to actually enhance strength and suddenly there are a lot more women with a good bit of OP strength (by AS standards) in the Tower.

I do think he's stayed more consistent with Talents and skill though. Even in the very beginning Siuan tells Nynaeve that with training no 1 Sister could block her from the source, and even in the above quote Moiraine stresses the importance of training.