Many very effective people have routines, so I'm not sure when it becomes a diagnostic feature. How does it feel to you when you are prevented from doing your routine?
I just finished reading how the daily monastic routine of the Benedictines was a tremendous support to a visiting poet... so the subject of routines and their function is front and center for me, too.
I noticed that when a friend of mine didn't reply within the usual time limit (3-4 days) my anxiety levels went through the roof. I didn't even realize that we had a routine, but it became very clear that at least I did. Wow.
So I think it may actually be difficulty dealing with a change in routine that is diagnostic, not having a routine in and of itself.