If the boss isn't a valid target ( focus target doesn't even show their name like the first boss in neverfun) or they have an invulnerability buff ( like living liquid during their taxis), wildfire won't deal it's damage.

Theres a lot more factors that can get in the way of a perfect wildfire versus( timing accommodations and having any other target in range means you are losing at least 100 potency off the bat) other jobs with its burst, and I'd say that it's the most detrimental dps loss if it does not run its full course (since the damage is dealt at the end versus it being spread throughout)