Giordano was a unicorn with a very strange career arc but even then he had a massive 58-point season in his second year in the AHL.
That said, yes, I agree that Rafferty could be an effective NHL player. As I said above, his puck skills, offensive IQ, and transition game are absolutely NHL-calibre and if he's sheltered in the right fashion on a 3rd pairing to hide his defensive issues I think there is reason to believe he could be a contributor for this team next season. But, again, the problem is how many young defenders who struggle defensively we're going to need to shelter.
My comment you're quoting was referring to Chatfield and Brisebois who both really struggle transitioning the puck and are both very unlikely to be NHL regulars as a result.