@Panini it seems you’ve hit the point of the game you decide how your build will look like and make tweaks for better performance. Also congrats on your max level build, nice! 
Devotions: Actually I find my route to be pretty balanced between defense and offense. Sure for super bosses you can go for more defensive one but DG is massive boost to your damage. Also gives some OA/DA, which as you mentioned can be problematic and actually is common thing for vitality casters. So DG/Rattosh is actually the most efficient map. Also looking at build mentioned I find hard to believe 2H build without Kraken devotion. 
But I should say linked build is Wildblood set, which hybridize vitality damage with bleeding, while Dark One have nothing to do with bleeding, so going Huntress isn’t optimal and having two sources of flat RR - Revenant and Scales is redundant.
Skull have pretty good mod, might be even better for sustain and more damage on top of pretty valuable stat for casters - cooldown reduction. Only significant advantage of shield is the chance of rolling physical resistance.