Criterion--> Duty Finder ---- Criterion Savage --> Raid Finder
I am wondering why Criterion can't be put under duty finder. They can do it exactly like the 8-man raid. The only difference here is 8-man vs 4-man. Normal Criterion's mechanics would have more visual indicators while Criterion Savage would have different and more difficult mechanics. The difficulty and rewards can be adjusted accordingly. Putting it under DF will very likely increase the clear rate whereby more people get to experience it. In the end, Roulette: Criterion can even be implemented if they want.
As for Variant, it can remain in the separate UI.