I'd like to point out that Pure Mortals can still kick an impressive amount of butt without magic - and Pure Mortals are liable to have a few extra Fate Points lying around to use on costly Stunts and Aspect tags.
And remember - being a Pure Mortal does not prevent significant amounts of *knowledge* in regards to the supernatural. A character who is, say, a folklorist could easily identify the exact nature of the supernatural threat, figure out the weaknesses thereof, and exploit the heck out of them.
(No, seriously, a Folklorist In The Know with a .50 cal rifle and custom bullets of assorted metals would be death on wheels...)