Dazed, stunned, and dominated become more prevelent at later levels as conditions that both the PC's and NPC's cause. So, if he is refering to a character in a higher level camapaign or a character throughout its current life then its not odd at all.
Mathematically it's astronomically against that happening. How many single characters have you played for 90 consecutive levels? Granted, the math I used was only from all three tiers of the Monster Manual and other books have other ratios of monsters with a Daze or Stun attack against Will, and/or his DM could be throwing Daze and Stun capable monsters at the group every encounter. But, the feat has only been out for what, 6 months?
Remember, he was only talking Daze and Stun, not Dominate. And, there are Fort attacks that do Daze and Stun as well, but he was only talking Will Defense versus those two specific conditions.
I'm not saying that it didn't happen to him, I'm just saying that the odds of it happening to anyone else are extremely small, so his example doesn't really illustrate his point.
Even if one monster in the normal five that the DM throws at the group does only a Daze or Stun vs. Will attack on every single round in every single encounter, that would be 1 attack in 5 being a Daze/Stun Will attack, 8 NPC attacks against a PC per encounter, 8 combat encounters per level, and 15% average bonus by Superior Will at Paragon; we're still talking 5 levels. Assuming of course that the PCs wouldn't wipe out such a foe in the first 2 rounds, so that makes it 20 levels to have this happen 9 times.
The odds are against it happening as frequently for anyone else.
I don't think it's accurate to just look at the monster list as a whole. You don't usually just go through the MM fighting one after another.
When playing a "themed" campaign, some types of attack may be temporarily more common. Think an "underdark" adventure where you're spending a level or two squaring off against a colony of Mind Flayers, for example. There is going to be a whole lot of dazing and stunning going on.
Theme or no theme, being saved from Stun or Daze 9 times due a single +2 to +4 is not something that going to happen to most PCs. And if the DM is throwing multiple Daze or Stun vs. Will opponents against the PCs in encounter after encounter, he's more or less forcing all of the players to take feats like Superior Will and basically removing feat choice selection from the hands of his players due to the deadliness of the campaign.
And if the DM is doing this, one has to wonder how many times the PC has gotten Dazed or Stunned because of good DM rolling in such a campaign.
Many of us have played encounters where a given foe can Stun multiple times in a single encounter and we learned that it is ZERO fun for the players. So, most reasonable DMs shy away from it. Daze is a different story, but Stunned is a condition that many DMs save for the proper moment (like climatic fights) and even then, it's not something that most DMs throw a lot of at the players.