Apologies for the double post, because I can't find the edit button. But it seems that you are right because there was a hotfix that nerfed it to 1.2 Direct Fire with 18% chance of ignition. Still, I think Greased has a slightly better ignition rate, however Incendiary can fire longer without reloading.
With your current data, of incendiary fire ignition chance improvement of overall 20% - it does come up on top:
Greased:
shots/sec: 26.672
fire ignition chance: 18% (0.18)
fires/sec: 26.672*0.18=4.8
Greased will ignite 4.8 fires per second.
Incendiary:
shots/sec: 11.669
fire ignition chance: 18% + 20% (0.18+0.2=0.38)
fires/sec: 11.669*0.38=4.43
Incendiary will ignite 4.43 fires per second.
That DOES mean that greased flamer would ignite more fires per second than the incendiary flamer.
However, it seems like most of you, if not all were a bit confused by muse's inability to keep stuff updated.
As evident in this thread-
https://gunsoficarus.com/community/forum/index.php/topic,4569.0.html that I made, about incendiary behavior. Which as you can see is supported by a person with code access:
Incendiary is in fact 25%. It seems that it is added on top before the roll for fire happens. After that, anything on the object taking damage that modifies fire chance (such as hydrogen) is then multiplied into the final chance to catch fire.
Now let's do the calculating again,
Greased wasn't affected by the fire ignition chance mistake, so we can count on it being
4.8 fires per second still.
Recalculation for incendiary:shots/sec: 11.669
fire ignition chance: 18% +
25% (0.18+
0.25=
0.43)
fires/sec: 11.669*
0.43=
5Incendiary will ignite
5 fires per second.