Yes, you can now solo Legion raids, and Blizzard has even updated the Legacy Loot system so that Legion raids use it.
One of my favorite things in playing World of Warcraft is what I call transmog farming, even though it isn't always for transmog items -- sometimes I'll go tear my way through Black Temple or Hellfire Citadel just because it's fun for me to blow up old content.
When someone can solo the end boss of the second most current raid, I sit up and take notice. Mione has done exactly that, soloing Normal Gul'dan after a grueling 1 hour and 9 minute fight.
While Mione can solo current (and harder!) content than most players are doing currently, like, you know, a full +19 Mythic dungeon, raid bosses still give a bit of trouble.