ES (with EB) is more superior than mana from design PoV

I think going eb is pretty cheap, at least short term. Last build i ahad used eb, it had skins of the lords with MoM keystone in it essentially making it a hybrid build with still pretty meh hp pool (high ev) with easier dps. On other builds i think you need somewhat more investment to surpass hp with same dps, but on higher end non-eb builds i believe are more powerfull. I also for some reason find it painful to get elreon rings to get going on normal builds.

I'm using Devouring Diadem on TS Deadeye.

Reservation efficiency is good, but EB is better, because it allows me to use a Divine Blessing aura. The only issue is that I can't generate Inspiration charges, as they require using actual mana.