Hoppers on Nations are slowed down to prevent lag issues. This is absolutely necessary and I've seen other Earth servers do it as well. However, to avoid impacting player experience, what those servers did was counterbalacing that by making hoppers move multiple items at a time instead of moving them one by one like they do in vanilla. For instance, if hoppers were twice as slow, they would transfer 2 items at a time. That way, hoppers cause less lag AND are just as effective as in vanilla.

On top of that, this requires no plugin at all. Since the server uses Spigot, the number of items hoppers move at a time can be tweaked via the "hopper-amount" property in the server's spigot.yml file.

I feel like this would be hugely beneficial, since the current configuration essentially makes high tier slimefun furnaces useless for smelting large quantities of materials given how much faster than the hoppers they are.
If hoppers are currently 4 times as slow, I suppose moving items by bunches of 4 would be fair enough, but I advocate increasing that number a bit to avoid bottlenecks with the slimefun furnaces.