POE 2 Infernal Legion not stacking with more minions

After reading about the improved infernal legion support, I decided to have a go with a build focused on it, and only put infernal legion to the test on act 1 cruel.
And although it causes fire damage dealt as ignitions, I taught it would stack with more minions, since it's every separated instance of minions dealing ignitions. And since the Infernal Hound's (fire damage dealt as )ignitions stacked with flame wall's (fire damage dealt as) ignitions, I believed everything would work out.
But damage testing on the Beira of the rotten pack (since I at least can see damage numbers), I noticed that the damage dealt in 10s between 1 and 2 minions with Infernal Legion didn't change all that much (couple 100s of the basic attacks), meaning infernal legion is counted only once for damage against a single target, and not counted per minion.
To further test, I invoked my Infernal Hound, and it's (fire damage dealt as) ignition stacked with the other minions Infernal Legion, but flame wall didn't work to deal fire damage as ignitions together with Legion (maybe because Infernal Legion's damage is higher than the flame wall, wall's ignitions gets negated).
Meaning it's a limitation on Infernal Legion to only count once for damage even if there are multiple minions with infernal legion nearby, making so that all the other minions (that are properly taking max% life as fire damage/s) are contributing with, just maybe, applying damage to a bigger area, and other forms of ignition (such as flame wall) also don't stack with Infernal Legion, but, for some reason, Infernal Hound's ignitions count for damage
https://youtu.be/9tIjlgqL0Os video of another testing, showing Infernal legion working together Infernal Hound, but not with flame wall.

After some further testing, it seems neither reduced fire res (coming from Flammability) nor more minion damage (coming from pain offering) are afecting Infernal Legion's damage, bringing into question if even increased minion damage is affecting Infernal Legion's damage.
Or other more difficult aspects to test, such as if increased minion area of effect would increase its radius from 1.5m.
If I was more advanced in the cruel acts to have access to lvl 3 support gems, I would also test if Searing Flame's increased magnitude to ignites and Fire Exposure would work with Infernal Legion. But considering the trend, it seems it wouldn't.

I want to use this gem, I want to play a minion life stack build but there are so many problems.

The first and biggest is being an ignite it doesn't stack, more burning minions doesn't mean more damage.

The second is the biggest minion you have is infernal hound which has infernal legion passively and see problem 1, they don't stack.

This makes this gem completely useless for an infernalist.