I disagree, skank tanking in vengeance is ok but you will have very poor rage management and your ravage reset only works with the right stance (not tank stance).
If you on the other hand skank dps as immortal, you get viable rage management, faster taunts, aoe acc debuffs, aoe heal debuffs and so on and so forth. Managed a 2.2k dps and a million + protection today as immortal with dps mods but...yeah screenshot button did its usual superb job and didnt work. Crits will be higher in immortal as well as far as i have seen.