I never ment to imply that it was taking me down that much through ALL of my defensives at the same time, and I guarantee you it doesnt ignore armor. And no, a lot of physical abilities dont do that. Physical abilities that ignore armor are very few and far between.......
As a dk, you rotate through your defensives, so you dont have gaps where you are relying purely on base mitigation to survive stuff. You might have Bone shield up, or you might have defile up, or moderate self shield, but you generally dont have ALL of those up at the same time. And other tanks have more different mitigation mechanics besides. I know I lose out on a lot of extra armor that Paladin / Warrior tanks get for having a shield, and I cant block, so there is different mitigation right there.
As for how much damage he hit for in Wrath, when it was live, and you didnt out gear it: He still hit like a fucking truck with smash. He may not have hit for 100% of a tanks hp (in raw, unmitigated damage), but it was probably pretty damn close. THAT WAS THE ENTIRE POINT OF THE MECHANIC: You ate a big hit, then kited him around while he enraged.
Seriously, I dont know how many times I need to explain this, but unless your tank is in absolutely crap gear, Tyrannus should never 1 shot a tank with Smash, unless your tank simply isnt actively mitigating at all, and is constantly sitting at half health or something............