If you're a tank in World of Warcraft you know what Vengeance is. Originally intended to allow tanks to keep up with increased DPS from improved gear with DPS stats on it while accumulating tanking gear that generally lacked those stats, it's turned into a means for tanking players to do chart topping DPS on some pulls (especially AoE ones with multiple tanked mobs). There's been a lot of discussion about what might happen with Vengeance in patch 5.4, and now we have our first look at what Blizzard is contemplating for the tanking specialization.
These changes are almost certainly aimed at reducing the very high DPS that we can see on trash pulls and boss fights with a great many streaming adds (such as Tortos' bats or the packs before Iron Qon) especially as we head into the final tier of gear for Mists of Pandaria, which would inflate these numbers even more. Raids that use tanks with the highest DPS tanks will probably feel these changes the most. As always, this is the PTR, so if you have an opinion on these changes getting on the test servers and testing them out is useful so you can give proper feedback.