...Or, from a slightly different point of view, the chargen mechanics contain traps, and many inexperienced or non-math-savvy players fall into them.
Pretty much. The thing is, in my opinion its a pretty obvious trap. If you have a Will defense that monsters can't miss, you should expect them to spam daze/stun/dominate on you.
This isn't hard to avoid. Lets take a Half-Elf Paladin as an example, one who boosts Wisdom and Charisma, with no stat to boost Fortitude and Reflex:
Level 1:
I use the stat array 16/14/14/13/10/8, giving my Paladin stats of Str10, Con16, Dex13, Int8, Wis14, Cha18. To boost my Reflex further, I choose to go with a Heavy Shield. My Defenses at level 1 are Fort 14/Ref 14/Will 15 and rock solid.
Level 10:
At levels 4 and 8 I boost Wis/Cha, leaving my Fort/Ref alone. Keeping a Heavy Shield and wearing a +2 neck item, my defenses are still solid at Fort 21/Ref 21/Will 23
Level 20
This is where it starts taking some work. I keep with the tradition of boosting Wis/Cha though my 13 Dex becomes 14 and gives me an extra point of Reflex(which I will lose at Epic) Here I take two feats to prop up defenses, those being Paragon Defenses(+1 to Fort/Ref/Will) and Shield Master(Shield gives +2 Fortitude). With a +4 neck item, my Defenses are Fort 31/Reflex 30/Will 32. Not spectacular, but not exploitable weaknesses. Without these feats, my defenses are Fort 28/Ref 29/Will 31. Not horrible, but a little low on Fort/Ref.
Level 30
At Epic I go Demigod, boosting Wis/Cha, and also boost Wis/Cha at 24 and 28. My level 30 stats are Str12, Con18, Dex15, Int10, Wis24, Cha 28. In Epic, I take three more feats to fix my defenses. I retrain Paragon Defenses into Robust Defense(+2 all), and also take Epic Fortitude and Epic Reflex(+4 to each, that stacks with Robust Defenses). With a +6 neck item, my final defenses are Fort 44/Ref 42/Will 43, and rock solid and ready for anything. Without these feats, my Defenses end up Fort 36, Ref 36(34 without shield), Will 41.
36 in Fortitude and Reflex at level 30 does not cut it.