Go for it!

I'll update the difficulty above (EDIT: actually below!).
Spoiler: it's outrageously high XD
EDIT 2:
Funnily enough, if my calculations are right the chances of Vala succeding once against Storm Fist with these obscene and increasing odds are still higher than those of succeeding twice against the boss.
Specifically,
11,19% vs Storm Fist
vs
9,20% vs the Boss
Although... I"m definitely overestimating the chances against Storm Fist here since there's a really high chance of getting despairs (almost 50%!) or 2 or more setbacks (upwards of 80%!) when rolling against him... so yeah. Maybe trying the Boss might be better in the end. Not sure.
(And the really relevant question is: Why would I even bother to do these calculations?? Who cares??
Probably just tired from work... lol)