There are abilities and gear that lower your crit requirement, but usually only by 1, so 5% higher chance of crit. I agree that your crit chance should go up as you get better, but only in relation to the skill of your opponent. Like I'm sure Bruce Lee could punch me exactly where he wants to 100% of the time, but not so much against Donny Yen. The pathfinder system sounds smart.
It's definitely possible for people who have mastered things to critically fail. How many times have you drunk water in your life? Millions of times? But every rare once in a while you mess it up so bad that you put water into your windpipe. That's a critical failure. But the chances of it happening when you've mastered something should certainly be far lower than 5%.