Mortals with stunts can end up being strong in a much wider range of things in a high refresh game. They can dump points into a lot of social and knowledge stunts and be hardcore there.
The problem is that they will never be as strong as a supe focused in a similar area at least far as combat goes.
After a mortal gets an apex skill, a +1 to hit, and a +2 to damage they are pretty much done.
Mortal sword guy (+7, weapon 4) fantastic weapons, sword 2, two stunts.
Compare that to a supe doing the same thing ( this is without even maxing it out)
Apex skill +6 , iop sword lvl 5, sup str. 4 dam
(+6, weapon 9) normally this guy also takes the +1 to attack but we will pretend he didn't
You can of course make the argument that mortals will get more fp and that will balance it out. That doesn't have much merit in my opinion. They can't afford to drop 2 fp every attack just to keep up with a supe. Especially when they can't afford to be hit if they want to keep breathing.
The mooks in our 18 lvl refresh game our blampires.
This doesn't even touch on wizards who can easily toss around +12weapon 12 at this level.
The mortal can be a hell of a lot more versatile, but he isn't the best at anything.