So there has been an issue since chromie time got introduced, that the introduction quests for some classes to legion have been impossible, as you need to use high lvl abilities.
I wanted to level a new Boomkin alt, and chose legion for the weapon and mog. Turns out, that in the artifact quest for the Scythe of Elune, “The Dark Riders” part 2, you have to cast Solar Beam to continue, as the entire hallway is blocked by a slow+damaging effect.
I researched the problem, and i couldn’t find a fix for it, so i decided to test some things myself, and the only thing out of 8 different potions and stat boosts that worked for me, was this method:
Use Dash, jump as far into the damaging area as possible, stay in Cat form, and when you almost die, use a Iron Horde Rejuvenation Potion. It heals enough that you can get through.
Sadly though, you will need some kind of interrupt here, i used Haymaker, as i fortunately was a Kul Tiran.
Hope this helped!
Original post adressing the issue on NA: