Just wanted to chime in to recommend the fix that I used which was simply deleting the ex3 folder in my FINAL FANTASY XIV Online > game > sqpack folder then running the launcher which forced it to redownload all the Shadowbringers content. I did this multiple times and each time I did it different things were broken and caused an immediate crash (the cutscenes for the Ishgardian Restoration are still bugged on my current version but luckily I own a PS4 so I was just able to go on there and watch them) but I've finally found a stable enough version that lets me play all the content I want to. PvP and hunts are still a bit sketchy with so many players around but using the DX9 version which seems to be more stable in general avoids the crashes. So I technically still have the problem but I've managed to find ways to work around it. SE still needs to fix their game.

You can read a more detailed version of the fix I just talked about and all my technical issues here.