Steve,

I do have a Paddy Richter tuned D at normal pitch which is useful for song accompaniment, but it is also useful for a few tunes as you say. I don't know the particular tunes you mentioned as I mostly play English stuff but I have been learning the St Kilda Wedding and it is needed for that one.

AC
I am coming to the conclusion that much of this argument about the different tunings is somewhat sterile. All the various tunings that have been mentioned are aimed at overcoming some perceived disadvantage of the standard Richter tuning and will suit the music for which they were developed. The Paddy Richter tuning happens to be the one that best suits the folk music of the British Isles because of the range of most of the tunes. For example a Paddy Richter tuned G harmonica works well for tunes in G, Em and A Dorian as it keeps the melody in the middle of the harmonica where it is at its best.

I considered the melody maker tuning which does give you two full octaves as you say, but the actual range is not quite right. It would probably be OK for playing in D and related modes, but not for G and overall it is easier if you are using the same pattern in different keys.

Here is Sam Hinton playing an Irish hornpipe using a harmonica in standard Richter Tuning. While he is able to bend down a whole tone to get the E in the first octave, it does not sound quite convincing to me and many probably would not be able to bend that much or that accurately, so the Paddy Richter tuning is preferable in that situation, though it will not suit other situations.