Energy shield speculation

[Baajikiil]

And that's a lot of gear dedicated to achieving something that a bit of max mana or mana regen might do more reliably (keep your mana high)

Or am I missing something?

Well, say you have 15% ES (slvl 2), and take 100 damage. ES will reduce the damage to 85, and you lose 30 mana points. Nightsmoke belt alone gives 50% damage returned as mana, or 42 mana back.

With one item you've gained a permanent 15% damage reduction vs all damage types(except poison/open wounds, perhaps others...). Not too shabby.

But also not too good. How many sorc players have +0 to their skills? Any more points in ES, and you start needing significantly more % damage returned as mana to keep even. I've considered using this setup for my melee sorc though.

I submit that ES is not designed for a sorc that get hits alot, but one that gets hit rarely and needs the extra seconds of life that the ES will give to escape(thus the mana regen will help make up for the loss).
It is quite useful in avoiding one hit kills as well.

Hang on though, how useful is this?

You are correct, it is not worth it at all to go for max ES and max damage returned as mana. I've crunched some of the numbers before when planning said melee sorc, and only at very low lvls of ES does mana returned make a significant impact.