Be careful when you read that, avoided hits (in our case Dodge/Miss) extend our current value of Vengeance, it doesn't increase it. Therefore, if you jump into a pull, pop SD, and dodge the first couple of attacks, you extend your current Vengeance... if you started at zero Vengeance, you'll be at zero after avoiding those attacks. You need that one initial hit to give your Vengeance a large boost, then avoiding attacks is less detrimental to your threat.
I've only had a couple issues with threat so far, usually in AoE against prot Warrior. But that's probably just me being awful. Otherwise I have a hard time staying lower on threat when I'm not currently tanking.
if only WoW had come out when I was a teenager. Back then online gaming consisted of text-based MUDs....I could type "kill orc" faster than any of my competition, brosephs, and played a mean giantman cleric.