I don’t remember his attack speed. But it is pretty high.
BiS gear from Blackwing Lair with 5/5 Anticipation puts you at about 410 Defense Skill.
You can pick up another 14 from the ZG enchants (7 each), putting you at about 424 or so.
The other thing is that Agility gives you Dodge, and plenty of your items have either Dodge %, Parry% or Block% on them.
As long as you are keeping Shield Block charges up, a Crit or Crush should be impossible even below 440 Defense Skill.
Besides, the last theorycrafting says that healing tanks that are stacking Stamina and Armor (EH) is easier, more predictable and wastes less mana in Vanilla/Classic. That’s a whole other conversation though.
The combat mechanics of what bosses do to tanks didn’t change at all from Vanilla to BC. Crits, Crushes, Parry hastened attacks… all that stayed the same.
The main thing that changed was that Defense on gear was basically everywhere. It was relatively easy to get to 490 Defense Skill through pre-Raid blues, there was no reason not to.
BC was the era where it was possible to become un-hittable or “Block Capped” as some people say. Defense on gear was sky high in later tiers, so through a specific set you could passively not need to ever push Shield Block to guarantee that you will not be Crushed because an attack can only Miss, or be Dodged, Parried or Blocked. If you remember, Sunwell has a zone-wide debuff to basically bring tanks back down to earth, Sunwell Radiance.
I still would not call 490 Defense Skill required in BC. Shield Block works the same way. If your natural avoidance through Defense, plus any Dodge from Agility added up + 75% chance to Block from Shield Block together are >= 100% you cannot be Crit or Crushed.