I had a difficult time deciding whether or not to move stalwart soul to level 40 mainly because I'm reverting abyssal drain back to how it was before the rework and added a little mp gain to unleash so our aoe would feel complete even without stalwart soul and moving it down would mean either a blank spot at level 72 or pushing other skills later. Abyssal drain was basically the second part of our aoe back then so I think this can work and stalwart soul at level 72 just makes it's usage more frequent.