AFAIK the Wisp proc’d skills don’t use player skill trees unlike every other proc item in LE and that should be a bug.
And imma be real, that doesn’t make sense with how it works ingame. It says spread your ignites not spread a certain number of ignites based on the distance of the enemy.
Also we already have spread poison and damned from Mark of the Rat in Profane Veil and it works properly… (edit: Also the poison spread on potion use for poison overload)
But I think no point discussing about the broken item. Hopefully EHG can decide on how it should work and properly rework/reword it by next patch.