You can, if you wish, perfect every skill. That said, perfecting every skill requires an investment of your time.

You have to decide whether that investment pays off. I would argue that you will become a better player if you don't bother perfecting skills at first because you can use that time learning:

tactics - by fighting a lot (even though you'll die a lot)
the world - eg where to find useful equipment, how to use the terrain to suit you etc.

When you delete a character, those 100%'s are gone. They might have benefitted you by helping to keep you alive to learn other things, but I myself believe that area knowledge and tactics do this better than 100%s.

When you have the area knowledge and tactics, you'll be able to decide for yourself whether you personally consider it worthwhile spending time perfecting skills. Some do, some don't. I would say though that 100% parry with a bad choice of weapon will probably be less effective than 80% parry with the optimum choice of weapon.