Only Energy shield, usefull?

I just started building my witch (hardcore) and was wondering if going really high ES really is worth it compared to getting armour as well?

I mean isn't damage reduced by armour before it is applied on your character?
Or is it just that you get so much ES that your effective health is still greater than if you tried to balance it with armour?

Don't get me wrong, I don't think ES is useless, just wondering if it is smart to go full ES.

-SCB

I'm too inexperienced to answer your question but try this thread [read between the complaints]:

http://www.pathofexile.com/forum/view-thread/58854

or the mechanics section to learn the difference between ES and Armour.