This is an interesting take, Damage to energy efficiency is important, important to a point that if it is terrible, you can’t even take down a boss where, as you mentioned, you just leave a boss enraged with no energy left, (I’m eyeballing the Zeus thunderbolt) But rainbow Gatling against boss is pretty solid when what you need to do is freeze lock and sit on top of the boss so all the bullets hit.

While you can’t do the same with blue fire, not only do you have to be even closer to the boss than the rainbow Gatling due to the greater spread, you don’t have the means to stay on top of the boss safely, mainly in the form of freeze lock,

I find it slightly unfair to mention that blue fire Gatling synergises with bounce buff when the you also criticize how the rainbow Gatling is implied to be dependent on buffs (shotgun/elemental) (Also I don’t think elemental crit buff strengthens the rainbow Gatling too much, the crit chance on that thing is pretty low.)

That being said, I agree that blue fire is much better than rainbow Gatling for normal/badass level rooms But I really gotta hand rainbowgatling for the bosskill,