Is defence from armour really needed?

I have been playing as my Hammerdin for a while now and decided to take a break from it. I chose to look up a guide for a druid from Mrllama but found it annoying to watch when he reached hell. This is due to seeing him on hell, lvl 69 and using the same stealth armour he had at lvl17 and also a lot of weak defensive equipment. His res was mediocre and yet he still took the same dmg that my Hammerdin takes, even though my defence was way higher than his and my equipment was mirroring my level. Surely, this can’t be right?

I like his guides and don’t want to be seen as a bad person in anyway but he should have been torn to shreds in hell with that gear he had on, yet he took the same dmg that I’ve been taking, and that’s with holy shield on as well.

Defense only affects the chance to get hit, doesn’t reduce damage taken. Also would help if you linked the video to know what kind of druid it was.
Generally casters try not to get hit so defense doesn’t really matter to them and then the fcr from Stealth is quite nice (also the +mana regen), while for Frenzy you have a huge hp pool and hope you have enough life steal to heal back.

Thanks for the reply. Sorry for no vid link, this is the vid - Highlight: D2 - DRUID GUIDED PLAYTHROUGH - Part HELL!! - ALSO WTH HALF PRICE BITS !HalfPriceBits - YouTube. He was a wind druid but he got insanely close for a spell caster meaning he got hit a lot in the video.
With regards to the comment that you made Avengerx, I understand that it only affects chance to get hit which is why I’m just saying that, it’s pretty bad that you can basically clear all of hell difficulty with act 1 poor gear and survive it. I remember upon release of the LOD version being required to farm gear to get through hell, but now it seems like any old junk will get you through no problem.