Why is Nidhogg's Rage not in Raid Finder?

[bounddreamer]

Please don't. Party finder is for learning - or it should be, at least. Duty finder is for when you don't need party finder to clear content.

[Souljacker]

Please don't. Party finder is for learning - or it should be, at least. Duty finder is for when you don't need party finder to clear content.

Then I suppose that they shouldn't have added the practice\phase\etc to the raid finder. I wonder why they did that?

I think you grossly misinterpret the purpose of the Duty Finder. It's for people who can't raid on a schedule, not for players who have already put all content on farm.