Here’s one of the threads I made about a year and a half ago when this became an issue.
Reading other posts, the legacy buff was active for level 50s, but was hotfixed later on in SL so that level 60s could use it too and actually stand some sort of miniscule chance because the raids got even harder as you continued to level and gear up.
Level 50’s ability to solo went into the toilet, but level 60 was a complete and absolute clownfest.