The game interface doesn't make this particularly clear, but dexterity is extremely important to warriors. Dexterity contributes a small amount to your AC, but its key role is in the chance-to-block formula. According to Jarulf's Guide, the chance to block a monster's attack is: Dex + 2·(clvl - mlvl) + bonus
. Monsters always have a small chance to hit you, regardless of your AC. However, they do not have a guaranteed chance to bypass blocking. Monsters' automatic hit is why super-high AC, as from a Godly Plate, is sometimes less useful than +dexterity items.
If your dexterity is high enough (which, in single player, may not be possible, but it's very possible in multiplayer), you can get "perfect block" - a state where you block every attack that can be blocked. This led to a style of play called the Low AC Warrior (LAW): a Warrior whose AC was so poor that monsters were guaranteed to land a hit, but whose dexterity was so high that he blocked every attack. As long as he didn't get into a state where an attack hit while he was not allowed to block, he was immune to physical damage. (Magical attacks cannot be blocked if you can resist them, and are often too numerous to block effectively anyway.) Aside from the challenge, the advantages of a LAW were that it was often easier to obtain the required +dexterity items than to obtain a good enough armor class and that he could pursue other bonuses with the remaining capacity.
Considering the most extreme case, a level 30 warrior facing a Hell difficulty Blood Knight (mlvl 60), you need (30 + 250 + (2 * (60 - 30)) = 340 AC to get a 0% chance to be hit. (Note that due to the auto-hit rule above, a monster always has a minimum of 15% chance to hit, rising 5% per floor past dlevel 13, so a 30% minimum on dlevel 16. Thus, 325 AC is just as good when you are on dlevel 13, and 310 AC is just as good by the time you reach dlevel 16.) In comparison, you need 160 dexterity to get perfect block. You will have 60 dexterity from maxing out your base stats, so you need +100 dexterity from items. This is still a difficult goal, but it can be achieved, especially if you dedicate your gear to this goal to the exclusion of other bonuses.
A "perfect" (maximum bonus) Godly Full Plate Mail would give you 75 +200% = 225 AC. Dexterity 60 will get you another (60 / 5) = 12 AC. That leaves 78 AC you need to get from your, +dexterity items, shield, and helm if you want "perfect" AC in the most extreme case. Even if you get there, you still need to worry about auto-hit.
In Hell difficulty, The Dark Lord has worse To Hit than a Blood Knight, due to integer overflow.
If you take a less extreme case (stay away from Hell difficulty Blood Knights until you are a higher level), the math becomes more favorable.
Thank you for perfectly breaking down the DEX and block formula. A lot of detail I had no idea about, I was wondering what my block chance was since from what I recall the character stat screen only shows chance to hit and not chance to block. I could be wrong though.