Some smaller things can and should be adjusted still, - some relatively powerful spells are available very early and if that is adjusted the situation will look much better.
I'm thinking that this problem can be solved by making skillbooks less random. Like, make a certain pool of low level skillbooks available in the early game areas, another pool of mid level skillbooks for the mid game, and another for most powerful ones for the end game. As I've said before, this will make sure that players have tried out all levels of skills.
However, general level restriction is still a good idea, because otherwise some players will just try to rush to a higher pool area asap just to get more powerful skillbooks from some vendor.
Stat restriction may not be such a bad idea either, because otherwise most powerful skills will become available to anyone who has spent at least 1 point in corresponding Way of the whatever. But, personally, I don't like it, because it yet again forces to specialize.
What would be better, I think, is to allow all skills if you have sufficient level and points invested in corresponding Way of the..., but make their power depend on stats. Like, for example:
A jack-of-all-trades dabbling in magic (aka. AD&D Bard type) may learn a fireball skill, but it will do much less damage than a fireball of a more intelligent scholar mage, who is dedicated solely to the Art.
Meaning, you can still play whomever you want, with whatever skills you want, but if you really want to make the most out of them you gotta hone those skills. And that's where primary stats come in.
