It would be hilarious
Elf mains would never go near another ledge again.
Neither would the wizards or the bounty hunters : P
Actually, I think that no damage taken related abilities should be triggered by friendly fire, or by shared damage curses in the chaos wastes.
In the chaos wastes, damage taken from The Lady of the Lake’s Vigil, Khaine’s Fury, etc., should not trigger abilities or boons like Gromil Curse, Caxuatn’s Frenzy, and neither should damage taken from curses like Slanesh’s damage over time or shared damage.
Stuff like this seems like a massive oversight.