I don't really get what's the real importance of armors or shields with damange reduced by 4 or 3. I had an armor with 48 + 78% def and I wondered if it would have been better a 60 with dam reduced by 4?

I believe the reduced damage helps you from getting stun locked. After the guy causes so much damage you get stunned. I'd stick with the 48 + 78% for the extra AC. If they were closer in AC i'd stick with the reduced damage.

I had an awesome full plate. 71AC + 142% Yesterday I found another (don't remember the prefix) with 73AC + 130% -4 Damage From Enemies. Theres about a 4AC difference, I think im going to stick with the 2nd one.

the -damage mods are fairly useless in D1, since they're just not large enough. When monsters are dealing 100+ damage in hell, and -4 or -6 is meaningless. They can be pretty helpful against ranged/elemental attacks; if you've got good resistance already, having some -damage makes bloodstars and dog spit and non-advocate mage attacks meaningless.

higher defense is useful, but only to a point; monsters in hell have a % of auto-to/hit that they'll always nail you regardless of your defense.
http://diablo2.diablowiki.net/Diablo_Levels#Hell_Monster_To.2FHit_Bonus

how much defense you need drops (slightly) at higher levels too, since your Clvl is factored into the monster to/hit equations. Some simple tables demonstrating that are on the character stats page.
http://diablo2.diablowiki.net/Diablo_Characters#Maximum_Defense

Thanks guys!

Also, what's your thoughts on Fastest Hit Recovery? As important as in D2?

I've always like using Scavenger's Carapace on Sorcerer, as they normally will negate any stun lock.

Vang, up to what clvl?

I usually make a tank mage until i find taj's light plate. I usually keep equipment to go from a tank/artillery mage depending on if im going to do laz/gorash runs or hell/hell. It gets a little annoying. I could really us an item importer/exporter for muling since I can't connect to B.net

It was a long time ago, but since he was my highest level character, 38.

I used an AAA, and a bountiful and a plentiful of Apoc since they can only get 12 charges on the AAA.

Since that was actually my main damage dealer, I decided against Naj's.

Back on topic, I didn't talk about Warriors, I'd go with highest defense, unless your able to hit the max block at your level with enough Dex. My warrior is 34 or 35, and handles NM quite well, but Hell I haven't even attempted yet, as I need some better equipment.