Delegated NS groups don't work when there's a Microsoft Server in the grid ...

[#1]

It even says so in the docs:

If a Grid has any Microsoft servers configured, delegation NS groups are not allowed and vice versa.

butbutbut ...

Why? Does that make any sense? Do people who have MS servers not need NS groups?

[#2]

I was told that even if you add Microsoft Servers, that is only a management function. The DNS forwarding to those servers is still necessary for DNS resolution.  Thus the error we get when trying to add "Cannot add Microsoft serves if delegation NS groups exist in the Grid" is an unexplained conundrum for me.  I tried creating a different view, but the NS groups are held for every view, it appears.  I still have no solution for this and having the same issue you are.