New MFer

[Caaroid]

Is "damage before resistances" used to work out how much mana to deplete? I seem to recall discussion on the topic, but I haven't used Energy Shield on a 1.10 sorc.

Yes, this is the reason why many feel that ES has been nerfed in 1.10 -- and for normally built sorceresses this is actually true. If I recall Jarulf's post correctly, the damage mecahnics go somehow like this:
(1). PVP penalty
(2) ES/Bone armor/Cyclone armor
(3) Straight damage reduction (MDR and DR) -- I am sure up to this point
(4) resistances
(5) % absorb
...

So if one puts too many points into ES, one's mana will take gargantuan hits. (Personal experience with my ES sorc: amongst the non-mana burning monsters, the most dangerous are the balrog infernos, since they melt your mana away like there's no tomorrow. I wish they were using the player skill Inferno -- if it is bugged for us, why not for them? :)

There is a guide at another site detailing the setup for an ES sorc, you can find a lot of useful info about ES in that article.