Except, assuming appropriate gear level for the encounter, I find most of these hard to agree with. Because when I see that my tanks died to Impale/FB, it was never JUST the unavoidable attack that killed them/me, it was the combination of a the large physical blow and the ordinary melee attack within a span of half a second or less. As long as special attacks are on a timer that's independent of boss melee attacks, it isn't the literal one shot that's a problem, its the quick double tap that's lethal. And the ordinary melee aspect of the double tap is most certainly affected by avoidance. Dodge the melee strike that at some point closely follows the impale, and you'll live. Ferocious Butt is the same way.
Maybe I've been lucky, but I can't remember Enraged Molten Spew ever being a problem of tank base durability. At that point in the fight all tanks are free to taunt around, split the spew, rotate cooldowns. There isn't another significant source of damage at that point, so the tank should have the full attention of all the healers. The special attack's payload isn't delivered instantly, but over 2.5s, so a large heal in this period will result in survival. Even given these, your odds of survival are lowest if Dreadmaw goes into his EMS a split-second after landing a melee attack - which avoidance will stand a chance of helping.
Freezing Strike is a little more complicated due to the stun effect. The base hit can be closely preceded by a melee hit as any other boss ability can, but the stun negates dodge/parry chance on the back end. The enchant in question is defense rating, not dodge, and AFAIK a mob can still MISS a stunned PC. So, roughly speaking, defense is about 2/3 as effective as it normally would be - but that is still not valueless as you state.
Now, will the 22 defense present a LARGE percentage increase in your survival chances? No. But then the 18 STA doesn't either, really, being as it would only have helped if the actual killing strike - whether the special attack or the avoidable melee - would have overkill less than what, 250 or so? Possible, but not very likely either given the sheer size and inherent randomness of the strike.
So you are comparing two small numbers here. Which means that the relative scale DOES, in fact matter. As scale matters, I take the one that's more valuable in terms of itemization. 22 DEF under most circumstances for me.
The number of times that one says something bears no correlation to its accuracy.