Enhancers will lower the damage to pec. with or without markup.
If you look at them from an eco point of view, damage to pec is not what you need to factor.
The more important factors are the mob, its regen, and the hitpoints, and the weapon used.
I see a huge difference in costs with 5 enhancers in on Aurli vs none. Its a big difference for sure, big enough that without enhancers, I would no doubt lose my ass up there, every run.
Many other mobs, damage enhancers do not make sense. I will on occasion throw in eco enhancers and that is a nice way to go too if you don't need the DPS for a quicker kill.
In my case with an as-147 tier 5, I am already pretty bad eco, worse with enhancers. If you look only at the gun.
But with enhancers I can kill many high regen mobs before they reach me. Saving more in other costs, than the loss of eco on my gun.
The benefits from enhancers are not direct. They save armor/fap decay, and any extra shots you would normally need to make up for the damage enhancer boost. (which contribute towards the regen suppression)
The break rate is random, but I like what Denis said, damage per second vs the original DPS or something, makes sense.
The break rate does seem to increase as you add enhancers, IE 5 tiers in vs 1 tier loaded. Which is why that sounds accurate.
Since returns are largely tied to decay spent, I am not surprised that there is a general boost to loot when using them, the decay from them should reflect in the return, even if diluted.
I certainly know that I get far more globals with my uneco high decay setup than any (L) I have tried. (Granted , I didn't give em a true long term test.)
Despite my uneco setup, I am overall up in hunting over 2 years.