Yes I agree with the analysis that Dzong is kinda a 5th unique component.
It's evolved from "Prophets can build Citadels" to something that, because of the numerous ways to buff Holy Site yields, is a strong economic component.
The history of playtesting this mod is to basically nerf it over and over again. Perhaps the reason this has not been so successful is because while the components look reasonable on paper, there is effectively one-too-many of them...
Tbh, I really like the Dzong and the Dob-Dob, but I'm personally not too attached to the Yak Pastures. Sure they're built on Mountains and give a Unique Luxury, but it doesn't really
feel that great to me. Mostly because they are kinda just like a Pasture++ built on mountains. I do like the Yak Resource tho, so the following idea.
What if you removed the Yak Pasture Improvement and made the Dzong into a proper Unique Component that also spawned the Yak Resource.
Here is a possible implementation:
Dzong - Replaces both the Holy Site and the Citadel. The Dzong has the yields and properties of both Citadel and Holy Site and gains +2 Food if built adjacent to a Mountain. May be built by both Great Prophets and Great Generals. When built adjacent to a Mountain Tile, it spawns a Yak Resource nearby.
The Dzong described above also shouldn't be able to be built on Mountain Tiles, since in my (quite humble) opinion that's quite broken. Since it can't gain the +2 Food from being built on a mountain anymore, it instead gains +2 Food when built adjacent to a Mountain.
Alternatively, perhaps
Dzongs could just provide a Yak Resource beneath their tile whenever they're built? This would be a much simpler implementation actually... I'm gonna leave the idea above since I spent quite a bit of time thinking that up, but this new idea has (in my eyes) the downside of still having Mountain Dzongs. Though the other idea has the benefit of Mountain Pastures for Tibet without giving them two unique improvements.