I have been having a crisis re. not the Agnus Dei.
More than one crisis.
Taking the setting of the Gloria as a whole (i.e. the three sections together) I find that the Domine Deus – as in the line Domine Deus, Agnus Dei, Filius Patris is not set properly in context/sequence. Furthermore, the tone of this section seems too sombre. Thinking about the Mass as a whole, this setting is more suitable for the “stand-alone” Agnus Dei of the full mass rather than the similar words included as part of the Gloria (which, for me, are a celebration of the taking away of the sins of the world).
The upshot is that I have decided that, although I am happier with the chorus sections of the Agnus Dei now, this piece has to be significantly changed – or be swapped for a completely new piece.
I am experimenting with a few things including abbreviating the piece significantly and also trying the option of including these words with the Quoniam (i.e. as a new “first verse” for this piece).