Hey !
Playing a lot of Ember, I think I understood why many players would be against a WoF "nerf", mostly because this strong ability is close to be Ember's only survival chance on high levels.
But the low-mid level issue still stands here : walking on a straight line and making everything burn with zero effort is a bad thing. It makes people lazy, other players tired, and most of game's content useless.
What I suggest :
On World On Fire :
Mostly keep