I realize that Storm has her fans, but she doesn't really work in Rumbles except in team fights, for three simple reasons:
1. She has no defense except aerial maneuverability, if she can get into the air.
2. She lacks superhuman reflexes.
3. No plot-induced stupidity in Rumbles.
So the ugly reality is that pretty much any normal person with a handgun would go 50/50 against Storm in a default Rumble scenario. Most Rumbles involve superhumans or at least people with superb training, which makes it even worse for Storm. This also explains why she is unlikely ever carry a solo title of greater duration than a few issues. Storm works okay in the X-Men because she is part of a team, and they can cover for each other.