Yeah, that doesn't make much sense. If you become everything, then what is left of you?
Or perhaps you envisage something like the Instumentality Project in Evangelion, which basically equates to obliteration of individuality?
That's something I can get behind as an objective.
If the dunyain need to dominate everything rather than just their own circumstance, why are they cloistered?
To me their objective is quite clearly described as seeking transcendental enlightenment, similar to many eastern spiritual traditions.
There, achieving the absolute means freeing your own soul from the endless repetition of causality.
The dunyain quest seems very similar to that of the Buddha, wherein enlightenment for the individual does not impact on the greater world at all - apart for the progress afforded by their teachings.
Edit: I think allusions to the gnostic tradition would be more aptly attributed to the mandate. Learned, altruistic mystics giving up their souls for the sake of the world and all that.
Dunyain seem unconcerned with spiritual matters such as damnation et al.