You know how you can only have 12 odd skills equipped? There is no reason why Geralt shouldn't learn all of the skills from all the classes by end game. You can't equip them all. At least if you learn all of the skills, you can test and mess around trying to figure out the best build by end game. And you're not locking content for next playthrough.
Well to be honest I do not mind that at all. Some skills are just useless. I hate games where I end up buying skills I never wanted because there is no other skill to invest in and I have too many skill points which I do not need, because everything left skilling is not worth it.
I also hate games where I end up having all the skills available to me.
The only problem I have - like I said - is that there are only 12 and not say... 16 or 18.... skills that you can have at the same time. King of makes me fearful of having to constantly switch skill-slots in order to be more "flexible", but I want to be flexible anyway, I want to make my character a hybrid.
The only thing I think they did well in terms of skills is the bonuses for skills of the same tree/color. If you think about it, a person that MAINLY levels one specific tree (swordsmanship, signs or alchemy) is very powerful in that particular category. To counter that they enabled the bonuses for skills of the same color. Meaning if you do a hybrid character (let's imagine with 4x4 +4x1 mutagens skills you do have 1 blue, 1 red, 1 (silver ?) and 1 greed slot group, which means equally spread alchemy, swordsmanship, signs and "other"/Witcher skills. It would mean you would be less powerful theoretically in every category, than people that actually level 1 skill-tree the most. BUT, and here is what I like, the bonuses mean you will get bonuses for every skill slot group making you - at least partially - "make up" that difference in power by having those bonuses. That would mean, you are skill a little bit less powerful in all trees, but therefore you ARE powerful enough in all trees in contrast to people who are VERY powerful in one, but less than average in the others. Which I like. It's active hybrid build support.
I still think 12 is not enough though... and I hope I do not have to switch around all the time