The east gully near the summit of Big St Joe is NOT class 5! No technical climbing experience or equipment is required for this route.
With proper route finding, it is class 4. Just take your time to find the path of least resistance. It is exposed and fairly steep but the holds are plentiful and good.
I have only climbed up it and I think it would be pretty spooky to descend it.
Don't let the above 5.6 description deter you from doing this route.