Blood Magic & Eldritch Battery with Energy Shield Interaction

Now Eldritch Battery protects Mana.
Which some people hate but I personally think it fits the theme better and looks great.
It takes off the energy shield before Mana when spells are cast.
Simple easy to understand yet adds depth to the game bravo.

Now when you take Blood Magic you GUT your Mana leaving you with only ES and Health.
Wouldn't it be simpler to also take from ES before health.
This explains better the energy shield cooldown on skill use even though it was never hit.
Also simplifies the use of blood magic as to run it requires SO many variables.
It's like the most complicated keystone when it shouldn't be.

Just makes it more intuitive.

While I don't find the functionality of your idea off, I also don't find the idea entirely useful. If you're running blood magic, you want more life regeneration, which makes the extra ES only useful if you're doing burst casting, like totems. For anything more sustained the ES is not worth the keystone investment because you want more life and life regeneration more than anything else -- because the life is far more defensive than your ES.

If anything the better option would be to keep ES with it's current function and make blood magic drain ES first anyway (because it already protects your life pool). But that might upset some low life builds. I assure you, high life blood magic chars wouldn't care, because the ES doesn't recharge anyway.