I like the Vengeance mechanic a lot. Seeing my AP scale up past 26k and topping the DPS on certain AoE pulls is a nice epeen boost for a role that doesn't often get to epeen.
And while Vengeance does solve the issue with threat scaling with gear for bosses that do enough damage to you to reach that cap, as bosses move to farm and gear improves past the point where boss damage is enough to cap Vengeance, once again our threat naturally declines as gear improves, while the damage classes only scale upwards.
At this point in the tier I'm finding that holding aggro on the pull has once again become an issue. So I've had to refocus on reforging for threat stats, taking myself to the expertise soft cap, and any other convenient stat trades for extra expertise or hit rating are at the moment easy choices to make.
I've also, for the first time in a long time, felt it necessary to shine a bright light onto my threat rotation, just to make sure that I am maximising my own damage, and I'm a bit ashamed at the significant improvement I've only recently achieved in this aspect.
This is all a temporary issue, I know, and once we're in Firelands and the bosses are smacking me as hard as I can take it I'll be back to reforging off as much expertise and hit rating as I can just to get a few more parrys in. But it's interesting to note all the same.
So, TO DO: get a mod that displays my current vengeance stack and/or total AP, because this is valuable information for a tank to track in order to manage threat output. Bonus points for having an awesome audio cue when it caps. Or, or, maybe awesome music that starts when it caps and stops when you drop below 80%. That would be neat.