Yes, that is my understanding as well. Energy Shield is applied and then resistances apply to the remaining damage after that. There are two ways to look at this:
1) Oh, good, if I have a high level ES I don't really need to worry about resists as much as a normal character since they only apply to the leftover bit. I can focus my equipment on +skills and other things instead of resists.
2) Rats, the amount of damage ES has to absorb is huge since it is applied before resists. I'd better have a good mana pool for ES to work OK, even with a high level of Telekinesis for the synergy.
Both viewpoints are valid, to my mind!
"Damage reduced by xx" and "Magic damage reduced by xx" are applied after ES, so those mods which are usually don't help much can help an ES build nicely, often more than resists can.