The Parry gear fight was exactly 6 minutes and 18 seconds. I'll have to re-load my logs from the Crit/Det gear fight to give you that ones exact timer.

Honestly though, the fight, no matter how long it takes, wipes you at 7 minutes. It's an enrage that hits the entire party for 25,000 damage. So Real world numbers say The boss has 532,000 HP, so that's how long the fight is. Time is irrelevant realistically. If your killing it faster, then you ARE mitigating better, and taxing your healers less.

The boss also has an innate DPS that is visible, but in the end, If the boss deals 2000 DPS for Example, and you kill it 30 seconds faster, then you just mitigated a theoretical 60,000 damage. If I recall, (Don't quote me on this, I'll get the real number soon) the T7 boss deals only 270 DPS on average. So if we kill her 30 seconds faster, that's a mitigation of 8.1K caused directly by increased damage being put out. (Strangely enough, that's almost exactly how much less I took in Parry gear.)

The reason I don't sacrifice Vitality for damage, is because that's a guaranteed safety net. My healers have reliable breathing room with each point of Vitality I gain. Sacrificing that for Strength is only useful if your healers don't need as much breathing room. So for this fight specifically, I would actually start to equip Dragoon gear as we gain in Party ilvls. Killing her faster saves us a LOT of headaches. I will be slowly swapping gear pieces in favor of Strength each week we clear it, until my healers tell me to stop. (I do EVERYTHING with their permission BTW, because I tank for my group, not for myself.)