Currently, for 1 hopper to transfer 1 full stack of items into another chest below it, takes about 1 minute and 42 seconds. In vanilla, normal MC, it takes about 26 seconds. This is a near 75% speed reduction, meaning for one full dub of items to move just to another full dub, it will take in total an hour and a half just to move 1 dub on nations. Sure, you can cut this time in half by having another hopper on the dub as an output, and it will bring the total time down to about 50 seconds per stack, but then you run into the issue of hopper limits per chunk fairly quickly, and 50 seconds per stack is still an extremely long time for a dub. (Further explaination below).
Im suggesting at least doubling the current hopper speed, if not bringing it closer to 75% of normal speed+. You then wouldnt have to wait that 90 minutes for one dub to move only ONE down, or have the server have to work that hopper for 90 minutes, it would only be 50% as much, or even shorter.
There is already a hopper limit, So increased speeds should match that because currently it is completely unfeasible to use hoppers for literally anything. For example, if you wanted to make a bulk storage for dusts/charcoal/etc, consisting of only 4 dubs, If you filled the top chest, it would take about 4 1/2 hours (102sec/stack*54stack=5508sec/60=91.8min*3=5 1/2hrs.) to go to the bottom using 1 hopper, compared to normal speeds using 1 hopper which would be about 70 minutes. Two hoppers along the entire bulk system would cut the time down in half respectively, Still being on Nations = 2.3hrs, and Vanilla = 35 Minutes.
A potential, but I dont know how feasible fix for this, could be each player has a set global "Hopper power". If you have one or two small farms, with x small amount of hoppers, they can be utilized at maximum efficiency, However, if you have a large, several chunk 250 hopper farm, then it is slowed down to x percent base value.
This would allow players looking to make one decent farm the ability to have good speeds, and "punish" players for having larger, more demanding farms. It would make players consider, do I really need to use 30 hoppers here, or could I get away with only using 15?
The scaling would look something like this, And this is my formal suggestion if possible-
https://gyazo.com/bb980b2a94ae561668554eed47275102