Saying people just want more damage is an oversimplification, we want more engaging rotations to deal said damage because there certainly isn't much tanking to be doing. However that is a feature for another expac because they wont make sweeping changes like that mid expac, what people want is a reason to feel relevant, and for a lot of people thats a larger slice of the damage pie. Even if bosses health increased around the fact that tanks had more output, I wouldn't care because it would feel like you have more of a presence when you're doing 75% of the damage of a dps not 50%, and it'd allow tanks to see bigger numbers in their rotations which is always fun. Increasing their max damage potential could also make a wider difference between a good tank and a bad tank.