I would much rather lose a fight because I was outmatched then because I got consistantly unlucky. I certinally wouldn't want said luck to play a major role in almost anything I did to the point where my own abilities are minor until mid-levels.
In that case, you may wish to roll different dice depending on the base skill in question. e.g:

1-4 ranks: 2d4
5-6 ranks: 2d6
7-8 ranks: 2d8, etc...

For criticals, I always favoured the notion that, if you hit at all, just roll to hit again, at a -4 penalty (modified by 'threat range'.) Repeat as neccesary, doubling damage each time. That'll cut them Hit Points down to size...
For another, its not just about reducing criticals and critical failures, its about using a bell curve to reduce the element of luck in general. Not only is this more realistic, but it makes for far better gameplay IMO.
As has been mentioned, a certain amount of luck IS realistic, but strictly speaking 2 dice don't give a bell curve so much as a pyramid.