I just don't get why you wouldn't join the discord if you want to do BA content. If you know people in the instance are trying to do a premade run, then why would you just barge into it if you don't even want to affiliate yourself with the discord? Why not wait for an instance without a discord group trying to do a run?

Anyone is welcome to join the discord. It isn't some exclusive club. But jumping into a portal (and forcing someone else out of the run, possibly a healer or a tank) and expecting people to accommodate you once inside is just silly. If you are completely clueless about what is going on that's one thing, but I find it hard to believe when these groups make it known in chat what is going on.