I don't really see how this is relevant. If your soloing a boss you're probably not taking vuln stacks to begin with.
As opposed to the people who died, who likely had 2-3 on them. I get you're trying to make this sound like I'm saying this is a skill thing, but I just said "normal content isnt hard for anyone". Anyone includes tanks.
Its nothing about talent to me, I queued for a thing and I'm going to do it. In turn I see no reason why you dictate how other players play the game due to ineptitude at normal mode mechanics.
I'll give you that Tanks are overkitted for normal content, but so are healers. And DPS aren't even tested in normal content.
Vuln stacks not mattering to tank is just how the game is to me, I'll avoid attacks that are actually lethal, and stand in the ones that give some form of benefit such as uptime.
I doubt they're in a rush to make the game actually hard for anyone at this level.