I presented in this thread all the reasons why I think Uruks are overpowered. But I more or less changed my mind about it, so I'm proposing a new suggestion, a debuff that will instead buff the Orc factions. There are other more complex and bigger suggestions out there that tackle this subject, but I'll settle for something simpler:
Gundabad
>> The current Gundabad Uruks keep their stats and their gear (maybe they could get a reskin with more advanced weapons and armor? In a Hobbit quote it's stated that Bolg's bodyguards used steel scimitars), but they are renamed to Fell Uruks or Gundabad Fell Uruks. They continue to spawn only in the Misty and the Grey Mountains, and sometimes on invasions.
>> New Uruks are added for the Gundabad faction, called "Gundabad Uruks" duh. They are stronger than Orcs but slightly weaker and shorter than humans. They spawn in Eriador, Dale, Anduin and all the other thousand places that normal Gundabad Orcs can spawn. See, Gundabad would actually get stronger!
Isengard
>> Uruk-hai get debuffed, they would be slightly weaker and shorter than humans. For obvious reasons their equipment would've to be nerfed too.
>> The strong (I'm trying not to use the word OP) Uruk-hai we currently have in the mod would be renamed to Half-orcs. They would spawn a bit more rarely and their skin would be a mix between Orc and Human.
This way the Rohirrim, which are severely underpowered in comparison with Isengard, would have a chance against normal Uruk-hai mobs. Meanwhile evil players would have access to the Half-orcs, strong NPCs like the Uruk-hai currently are.
Mordor
>> Black Uruks keep being Black Uruks, but they don't spawn outside Mordor.
>> A new generic Uruk is added to Mordor, which can rival Human NPCs in terms of stats and gear.
Overall the Orc factions would be debuffed, but players from these factions would still have strong NPCs at their disposal, while being lore-friendly (somewhat) and keeping the game balanced.