Wildfire is not behaving as the description reads. Enemies are never reaching more than 4 stacks of Soulblaze
Stand two enemies near eachother.
Apply high amount of soulblaze with purgatus staff to one and kill it.
4 Stacks on main target.
Spawn another enemy and repeat applying high warpfire and killing
No further stacks on main target.
From the description it would be expected that the second kill would allow the stack size to increase up to 8, but it never exceeds 4.
When a target dies, it will spread up to 4 stacks on nearby enemies
The stacks on the spread targets cannot exceed the stacks on the dying target
What the description doesn’t tell you is:
That spread radius is 5m
The stacks have to be 2 or more on the dying enemy in order to spread (another bug report already exists)
The stacks on the spread targets cannot exceed 4 in any case
That is, let us have enemy A with 8 stacks and a nearby enemy B with 6 stacks. Enemy A dies. Based on the description, it is expected that enemy B will get 2 stacks and bumped to 8 stacks total. A can spread 4 stacks but the stack count on B cannot exceed 8 so only 2 stacks speed. What happens in reality is nothing because B has more than 4 stacks, even the duration is not refreshed.
The description in no way expresses that it maxes out at 4 stacks possible in total and does nothing to enemies already at 4 stacks. The way its worded makes it sound like an enemy dying at 8 stacks should be able to bring another single enemy from 4 to 8, or to bring 4 separate enemies from 4 to 5.