Why a tank need to dps at all?

[Shurrikhan]

Better not get in a group with me then. I am there to tank and keep aggro not dps. I do not dps on my tanks, if I want to dps then I will go on a dps job.

There is no requirement to dps as a tank, our job is to keep aggro so they can do their job.

There will come a time when you survive based on the duration, not just the severity, of your and your healer's cooldowns. Should the fight end before your eHP, given HPS, bottoms out, you win. If you do not, you die, and your party shortly thereafter. At that point, lying dead, a thought may occur to you—"had I dealt 400 more dps, I'd have been taking would be taking 30% less damage at the end of that trailing Foresight due to all the smaller mobs having been dead", and your healer will likely be having the thought "well, if I knew he was going to make me overheal the first 8 seconds, I would have AoEed for its added mitigation."

Well, probably not, because for you damage, mitigation, and healing required are apparently somehow separate, despite that each determines the other...
And this works in every direction. If a DPS fails to burn down an especially deadly mob in time, you can't just pin that on the tank and healer when the tank dies and the party follows. That survival "role" falls on the DPS, too.

So please, stop purposely taking your "role" out of context. They don't even exist. Only toolkits do, and accordant conventions.