First of all I'll say that, if the zeny/hour of geffenia mentioned in discussions/guides are correct, then I don't believe the zeny/hour there is that OP, some other maps have better ceiling. That's why I don't believe this is as big of a problem as people are making it out to be.
Despite that, there are 2 reasons for why the geffenia may still be considered problematic:
- It's likely true that geffenia causes inflation due to how the entirety of the income there is "raw zeny", as opposed to other farm maps where the majority of the income is from other materials. And due to its ease-of-access. I assume high inflation is not something that is good for the server.
- Generally in game design, doing more challenging tasks tend to be more rewarding, for a good reason. It doesn't make much sense how one of the easiest maps in the entire game that is just a remnant from pre-renewal times is one of the best places to farm, better than most of the newer maps that require way more effort to farm.
With that said, I think making custom nerfs to illusion doping would be unfair, and is not a good solution. I don't like that idea even though I personally hate that skill. Specifically nerfing only geffenia mobs is also not a very good solution imo.
If GMs consider the current state of geffenia a problem, then a better way to go about it would be to simply tweak the formula of zeny dropped from the monsters. Currently this feature probably gives more zeny than they intended there since biolos one-shot an entire screen of mobs every second. Since this is a custom feature specific to MuhRO, GMs have every right to modify it as they see necessary anyway.
IIRC the zeny-per-mob formula already scales based on monster level. It could be slightly tweaked so that it gives less zeny for very low level monsters, but goes back to the current values after around lvl120 or 130-ish.
(Geffenia mobs are between lvl100~120, old thanatos mobs are around lvl120~130 , and all the other important mobs that people tend to farm have way higher levels)
