I wouldn't call gauntlet useless outside of classes specialized in it : having that brave effect is nothing to scoff at (and I still hold on the theory that brave weapons won't return for this game).
Anyway, the only time it would make sense to choose your strength/weakness would be when you choose your gender, name & birthday. But in this video below, that doesn't happen.
first time meeting Sothis (french)
So either you cannot choose them at all, or it is somehow affected by your birthday (the later would be kind of dumb, though).