Your current threat level is irrelevant when you taunt. It brings you up to the threat level of the person with aggro and gives you aggro. It's what you do immediately after that determines if you stay ahead. The other tank only has to reach 110% of your threat to take the mob's aggro back. Since he has a large stack of vengeance, it's very easy for him to do, especially while you're just starting to stack vengeance back up. For that reason, it helps if the tank who is not tanking cools down a bit for the first few second after the taunt before starting back into the full rotation. Usually when my offtank taunts off me, I use a couple global cooldowns to drop a Demo Shout and a Thunderclap on the boss before even considering a Shield Slam. If the tank you're tanking with isn't helping you like this, it could make things more difficult for everyone.
Originally Posted by Michultradk
Kathy, I said, "I'm lost" though I knew she was sleeping
I'm empty and aching and I don't know why
Counting the cars on the New Jersey Turnpike
They've all gone to look for America