I was a little disappointed by this also. I think they had a lot to work with there and I am a sucker for a bad guy that I can relate to in some way. Kind of like Iago from Othello. At first you think that he is so evil because he was looked over for a promotion, but n reality he was jealous of Othello, because he believed he slept with his wife....It made me hate Iago a little less. Instead, we got a being who wanted to take godhood for himself, for no apparent reason other then power...
I agree I would have loved more development on Corypenis. However, it makes me wonder why they chose not to. They really spared no expense at deepening the rest of our lore library and adding in new layers to the world. And Solas, and many others, are so well-written and dynamic. Which makes me wonder ...
That note in the Fade made it seem like Corypenis' entire mentality changed after exposure to ... something. So what if entering the Black City was not what started the taint and instead was a form of possession. Corypenis was unlucky enough to have been exposed along with the other Magisters. So they enter the Black City and ... strengthen the power of whatever is trapped there.
So I guess my point is that maybe Corypenis did not get plot development, because he truly is that single minded. He's possessed. To reveal more than that would cause the writers to "show their hand" and let slip what happened in the Black City. I think that eventually we will understand exactly what happened and then we'll look back at Corypenis and go "Oh, I get it."
I hope so. Of course I have fully indulged in the Well of Bioware and drank the koolaid. So don't mind me.