Blizzard made a mistake with vengeance having no cap in MoP. On several fights tanks are pulling actually bigger numbers than most of dps and it's not an issue of dps' skill.
http://worldoflogs.com/rankings/players/Mogu'shan_Vaults/Elegon/25N/dps/ <- out of top 10 dpses on Elegon, 4 are tanks
http://worldoflogs.com/rankings/players/Mogu'shan_Vaults/The_Spirit_Kings/25N/dps/ <- out of top 10 dpses on Spirit kings, 6 are tanks. Whole top5 are tanks.
http://worldoflogs.com/rankings/players/Mogu'shan_Vaults/Feng_The_Accursed/25N/dps/ <- top 10 dpses on Feng, 9 tanks
In my opinion it's silly. It diminishes fun of playing a dps, seeing tanks doing more damage than you. Do you think blizzard should fix it and put a vengeance cap back on?