Hi there! Since our server got mentioned by name, I thought that I should explain what our server did with Banapaty and with Elunium for a low rate.
Sadly our wiki is not as updated as we like for things outside of the gear department, so Banaspaty is missing the Freya Crown drop, an item exclusive to Star Gladiators when we gave all classes a custom equip set to boost either forgotten, ill-supported builds like blitz beat hunter, or just classes that need attention in general like Star Gladiator. We just happened to spread out those gears across a ton of dungeons so that most of the pieces are either from mobs that make sense for that class to hunt, or they are just spread out to encourage people to go to different places like here.
Coal is indeed higher than anywhere but Steel can still be a nuisance to make, and not like crafting is very useful besides as starter gears (we'll customize that some day when we have the time.) So we are actively ok with any possible over-abundance of coal if that's what will help the few remaining blacksmith to forge.
Now as for the elunium vs oridecon situation: all MVPs in heRO drop either both elunium/oridecon, or has it moved to their mvp drop so our mvpers have their supply in roughly equal number of the two. As for things that drop ~15% at our 3x drop rate (5% at 1x), it's only the minibosses or challenging mobs at 40k-60k hp range that reach that drop rate. We always try to maintain the same base line and difficulty expectation.
Our server actually sort of has the opposite where elunium and oridecon are roughly in same supply, and oridecon is being used up by a particular forger burning through them so much that it's favoring elunium in availability. Although each individual monster has roughly the same drop rate, elunium just happens to be in spots that are eternally "need to be farmed" like raydric and khalitzburg as you said. Though no monsters standout, we also just dripped in Elunium at classic 2-4% (at 3x, so 0.5 to 1.2% at 1x) rate on new custom monsters that may serve to be new leveling spots like in our Lutia region. On the other hand, oridecon used to be from geffen dungeon mobbing nightmares and deviruchi. However, infiltrator has aged poorly to BG gears. Blue herbs got new sources now than nightmares. Even with heRO customs providing some incentives, not much people go to mob geffen anymore so Oridecon is not as readily available in 2020 as say 2010.
At least to our server's meta, Abyss Knight and geffenia are also still extremely contested to get the AK cards, and AK provide both at once as well. This results in a situation where Elunium almost always passively gets added to the economy, while oridecon requires more effort than elunium to reach the same effect (only got mvps and AKs).
Finally, our server also has a lot of customs, and generally there's much more custom weapons than armor. Custom weapons require you to spend your oridecon for every class (with few rare exceptions like daggers that can get used by multiple classes), while your armor is probably shared between all your characters. Because of our customization, we mitigate a huge part of the problem you described where you end up with having tons of armor to upgrade but not weapon. If you think there's not enough things to use oridecon on, then naturally the server can provide you with some customs to think about

I certainly didn't expect people to have interest in pre-renewal Dewata in particular. In heRO, we end up using the field for Alnoldi leveling the most since it's customized to be a slow, still moving plant for us with decent usable drops and is a natural next step from the immovable plants for casters. So if there's other servers with interesting ways to develop Tina Grace cave, I'll be interested to hear it. For us, we try to add new drops to almost every monster: such that there's an "easy" source at a lower drop rate, or there's a "hard" source that's more challenging but it has the item at a higher drop rate. That way newer players can still farm it with hard work, and established players can go for efficiency at places that either requires gears, or is part of the WoE reward since the higher rate is behind guild dungeons.