No, but remember that Vorena had faith that Vorenus would forgive them, and her mother told her that he would kill them all

I believe that if he was told everything by Niobe (she could have confessed it to him) he would have not killed anyone. There would have been a big deal about it, but nobody would have died.

If the curse is just words - and the characters believe it too - then Vorenus has nothing to feel guilty

I think this is just my own perception. Because I am quite dramatic myself, I don't particular grudge him the words. And if he was there at the time Erastes arrived to his house, Vorenus just wold have been killed because he didn't have any protection from Caesar anymore and was alone.