^Well, yeah, but if Omega wanted a black hole potent enough to power all of Time Lord civilization, he wouldn't have gone for a dinky yellow dwarf, but for something far more massive.
That would be a galactic core black hole perhaps.
Now I can't help but wonder if some of the classic Dr. Who--and even the newer ones--still mistake galaxy for star system. In Genesis of the Daleks, we hear about seven galaxies. I think that was star systems.
With the recent Cybermen episode, we see a hole in space. I'm still saying the Desolator destroyed only a star system.
To blow up a whole actual galaxy? good grief!