Mortar Totems for Compounding Ignite?

Spoilers are hiding context. Should make it easier to see the TLDR.

!Firstly, I'm a long time player and have always loved fire damage in OTHER games. This is the first league I've seen a proper fire mechanic that makes sense and does as much damage as fire usually does in other games. So I'm really excited, but am also expecting nerfs for builds that are using compounding ignite via Flame Breath and Incinerate.!<

!Secondly, I always prefer making my own builds and usually heavily question the meta. But, we're about halfway through the league and I cannot even find a single mention of anyone using Mortar Cannon to passively spread the ignite through oil grenade, instead of manually using oil grenade yourself.!<

My thinking is...

• "Once Ignited, Oil Ground adds 150% of this Attack's Fire Damage as unscalable Damage to the Ignite" from each projectile from Oil Grenade increases the damage of the ignite
• So spamming Oil Grenade projectiles as much as possible via cooldown and Mortar Cannon both passively spreads the ignite AND increases the damage of the original ignite from Incinerate>! or Flame Breath (I wish >_>)!<

So, question for my fellow 1k hrs+ exiles, y u no spread ignite via mortar cannon??

Specifically, why is ramping up the damage of Incinerate the play compared to spamming Oil Grenade, especially w/ Mortar Cannons

!PS: I tried using Flame Breath as the ignite source, but the negative ignite magnitude causes way too much damage to be lost and therefore the need to ramp up damage much more. I am now very upset that my giant dragon breath attack is crap compared to a little hand wave animation. I -really- wanted Flame Breath to be useful for this kind of build because it's such a better skill than incinerate by every aspect in my opinion, especially the fact that you can ramp up the damage for both Flame Breath and Oil Grenade with attack focused passives and Warcries. Oh well :/!<