I think the problem is more that nif2 is abundant with drops that is valuable like zelunium, shadowdecon, etel dust, and Bloody branch. And the fact that it is still one of the best spot to farm the zelunium, shadowdecon, and etel dust beside BB.
Nif 2 right now is used for those that:
- Person trying to farm Bloody branch with shadowdecon/zelunium being a bonus
- Person trying to farm shadowdecon/zelunium with BB being a bonus
Before the ctb mob reduction patch (thanks kro /s), there was some people that actually farm that place for the shadowdecon/zelunium even without BB being dropped there but after the patch nif2 is better place to farm. There is no zelunium/shadowdecon drop rate nerf here but the mob density is reduced.
For other farming place like ami2 for example might have second best drop rate than nif2 but it is still second best and not the best one (which is still nif2 mob).
Mjolnir BB drop rate is a bit better than nif 2 but the mob there hits much harder compared to nif2 (with magic spamming and ignition break shenanigans) and the other drop is not as valuable as nif2 which makes the slight boost drop rate in BB is not worth it.
But this is like imo maybe there's sekrit spot that we might not know 😆
Also this is just talking about zelunium/shadowdecon. For zeny gain there is option just like what aewuu said like biosphere A/B, varmundt depths, geffenia (we never really move on from mastela farming)