The changes that they're making are intended to address this. We'll see where the lack of "bonus armor/trinkets" come into play, but the 20% multiplier increase should provide an across-the-board mitigation increase, should we take hits.
Also, due to the fact that IBF and BS lower damage by 50 and 40% respectively, it also gives the illusion that we're spiking even more. It's one thing to be regularly taking, say 10% more damage. You'll notice it, but you'll adapt to it over the course of a fight. But, if you go from taking 10% more damage than a warrior/paladin, to then reducing the damage you take by half, then going up again.. the healers have to watch your cooldowns as much as you do if they want to accurately predict (as opposed to spamming heals).
Edit: So, it's the both the fact that we're taking less damage with no cooldowns up, but also the fact that our cooldowns don't reduce as much damage that will make DK's less spiky.
Luck is what happens when preparation meets opportunity. -Seneca
Everyone marvels at a square egg, but only the chicken understands the PAIN.