Oil Grenade sometimes does not ignite

I have been having this issue with Oil Grenade not igniting enemies randomly even as the ground is burning, even enemies standing in it when it ignites and subsequent enemies walking into the bugged patch. Sometimes it does, sometimes it doesn't. It is very intermittent so its hard to reproduce but I have some ideas.

My current setup is Oil Grenade with Persistence, Magnify, and the new Suffuse support gem. I then ignite with Explosive Shot with Fire Infusion, Primal Armaments, and Auto Reload. I am playing a Hulking Form Titan with Resolute Technique.

What I have noticed is that if I shoot an oil grenade and either hit an enemy and then fire explosive shit, or shoot the grenade with explosive shot, it ignites just fine. But if I then fire another grenade at a separate pack some distance away and the burning ground from the oil touches the new area and ignites it, sometimes it doesn't ignite the enemies standing in it. Sometimes I feel like it might be happening when I ignite a third oil patch using the second burning ground oil patch.

I am thinking it might have something to do with the new Suffuse support because it creates a variance in the area size and its the only thing that really changes the skill because sometimes it works and sometimes it doesn't.

I am interested in learning more about this as well. I have experienced the same inconsistency. Oil grenade, once ignited, should presumably ignite enemies that walk in the burning area because they are A) covered in oil that is flammable, and B) that oil is now on fire and presumably "ignited".

Not sure how ignite would be applied by oil grenade otherwise because it's not doing damage on it's own in order to cause ignite - or maybe I am missing something?