Okay then you are saying that in HC that vitality is so much keen that the players do not have any main stat on their gear at all. Virtually zero IAS, CC, CD on their gear as well. Where they have nothing but all defensive stats stacked to the stars.
Look the gearing is different in HC, I fully understand it. But in reality the cut offs are different. But they still exist. If you have a piece of gear that boost life by 5k but decreases damage by 15k would you put on that piece of gear? If yes then I guess I would see in HC players that have around 750k life, but only 20k dps right.
When I say cut offs I am talking about from a mathematical stand point. There would have to be a limit to how much of one stat you would need in order to survive. It is there that the cut off exists.
There will always be a cut off point in any system of stats. Where that cut off is and how much will be different when consider both SC and HC, classes, and specs.
There cannot be a cutoff from a mathematical standpoint, because that implies objectivity in the requirement of a stat to survive. A mathematical cutoff is an objective threshold. However, how much survivability a person needs in order to live depends on their play style, their build, and how comfortable the individual is. In HC, unlike in SC, you will see different people needing different amounts of survivability for their own comfort. My DH has survived just fine with ~700k EHP, yet you will find people who claim that you require at least 1M EHP on a DH in order to be safe.
In HC, both DPS and EHP are unbounded in their necessity. Just because a person would gladly trade a little bit of life for a lot of DPS, that doesn't mean they're still not constantly seeking to upgrade their life. They would make the trade, but seek an option where both EHP and DPS can take a bump. The necessity for each thing is unbounded, yet the limited resource provided by gear is what forces hand to a difficult choice.
There has to be a mathematical cut off in all areas of stats. A point where your build has more than enough survivability to survive whatever the game throws at them. But at the same time your need for more dps would go up. Since SC has cut offs, then the same is true for HC. The only difference is that the cut offs are different.
Where on SC you can go all out with dps and be a glass cannon and not worry about death. Where as HC you are forced to be more tank like. And have a higher than normal defensive stats. But still your dps has to be good, or the mobs would whittle down your life till you are dead. That death would be due to having such a low dps that you are tickling the mobs.
I wish I knew theorycrafting math so I could show you the difference in raw numbers what I mean. But alas I cannot because I do not know the math. I think I would have to learn calculus and that would take a really long time to learn it.
Just like there is a mathematical best build and gear choice in SC, the same is true for HC. The only thing that changes is you have to be more defensive in HC than SC.
Now the problem here is does each player use the most optimal approach to gearing their character? The answer here is no they do not. Some go all out in SC and are a glass cannon. Then come here and complain about getting killed. When all they have to do is add in a little survivability to their gear and they would be good to go. Then you have the other side of the coin where you have ones that have built a tank and hit like a wet noodle. They will survive, but even they will complain because it takes such a long time to kill the mobs.