If the DM gets physically wounded for presenting even the slightest of challenge then the players aren't mature enough for the game anyway
Let's do the numbers then, shall we? Let's say, level 16 Paragon characters. Those guys are pretty powerful and up for challenges, right?
Now, the Wizard (leather armor)/Rogue/Archer Ranger that have high DEX and INT (assuming 18 and pumping it up to 22 by 16th level) will have about a 24 AC assuming they were wearing nothing. If the Wizard never upgraded to leather, and instead wore Cloth, then we might be looking at something on the order of a +4 Feyweave (+1 AC) for a total of 29 AC.
Now, let's look at everyone else (ie- Fighter, Paladin, Warlord, etc...) For those that didn't invest in DEX at all, we're talking a straight 18 AC. That's 10+1/2 level, and that's it.
So, the spread in armor classes here is a 6, with a high of 11 for the Feyweave wearing Wizard.
Now, let's look at the monsters they might be fighting:
Savage Minotaur (16 Brute) - The Savage Minotaur hits at a +19 to AC. For the guys with no DEX, this means an auto-hit on anything other than a 1, since they only have 18 AC. So basically, they will be hit
every single round unless that Minotaur whiffs on a 1. For a Brute, don't you think that's going to hurt a bit? Against that 24 AC though, he's hitting on a 5. Still really good, but at least there's a
chance that he'll miss against them. The Wizard, with his 29 AC from the Feyweave, will likely be fine though. He'll get hit on a 10 or higher, which is about 55% of the time. That's not too bad considering that he's only wearing cloth armor and not a frontline PC.
Abyssal Ghoul (16 Skirmisher) - This guy is at a +21 versus AC. He'll hit the non-DEX PC's automatically on anything but a 1, and the DEX PC's on a 3. The Feyweave Wizard will get hit on an 8, which is pretty good, but this is a skirmisher and that's a melee attack. It
should be pretty good against a cloth wearing Wizard.
Cyclops Hewer (16 Soldier) - As a soldier, he's got a pretty good to-hit. Namely, a +23 vs AC. That means that he hits everyone
but the Feyweave Wizard on a 2 or better. So, send a couple of these guys in and good luck escaping from the encounter with your life.
Edit: Before someone says something, I just wanted to say that I'm aware that I didn't include examples of something like a Fighter with 14 DEX and such. I did this to make the examples a little easier. With the low end of no DEX mod and the high end of a +6 from a 22 DEX (the highest the majority of players would have, unless they actually took a 20 at character creation) I felt it was pretty easy to see what the range should look like. Plus, against that Cyclops Hewer, only a 24 DEX would actually get you anything, since otherwise he'll hit anything else on a 2 or better.