I do the mythic night hold with my hunter friend. Neither of us could do it solo due to different issues we were experiencing for our classes. Guldan/Illidan is the only hard part in there and it kept tripping me up solo.
Mythic dungeon BFA run for mounts though, they are a lot less annoying than a few of legion mythic raids.
There is one area I won’t go into anymore… Legion’s Odin’s raid on any difficulty because of the mechanics on the first boss (got to pull mobs about to certain spots and get the boss duo down before they self heal to full.) Last time I tried that one i got into the situation of: they couldn’t kill me and I couldn’t kill them due to damage suppression, timing and mobs being annoying to pull about accurately on time. I had to close the client and use the stuck character service to get out of dodge.