How long should it take for legacy content to be completely soloable?

It’s no secret that I enjoy the whole ‘go back to older content and mess it up hard by myself for transmog gear’ aspect of World of Warcraft, because I just do not ever shut up about it. I mean, here we are and here I am talking about it again. But one thing that comes to mind for me is when I can comfortably solo older content, and when other classes and specs can do that, and how long too soon is when it comes to being able to power through the old stuff.

I think most players might say that it’s too soon for any but the most dedicated soloers to be able to go back and wreck Mythic Jailer, for example. I personally would not. I would be fine if any level 70 in quest greens could wipe the floor with him, but I do understand why some raid fights have mechanics that are solo unfriendly. I mean, Kil’Jaeden from Tomb of Sargeras in Legion is still pretty hard because he was designed with specific mechanics to challenge an entire raid group and those mechanics aren’t just about raw damage or how much you can heal for, they’re about coordination of a group and a solo player isn’t a group.

So I’m always wondering what the balance is and what it should be — are there fights in older content that still give you fits, like the tail end of Uldir does to me? Do you feel like maybe it’s too easy for people to run content that once required a bunch of other players and that it should be even harder than it is? What’s the sweet spot for how soon it’s feasible to solo legacy content in World of Warcraft?