I think there was a lot of hope on Zaitsev, who was played in the #2 role in his rookie year and was a little out of his depth but didn't get buried like Santini, that he would take a step forward in his 2nd year and be passable as a #2D. It went the other way for sure in his 2nd year, so I think there was a lot of backtracking on that opinion by those who had it. I don't believe he thinks fast enough to be a top pairing guy, but I could see him being a good 2nd pairing guy
I do think Voynov is an upgrade on the Leafs' situation, if he was a real #2 I would do it if he agreed to things that would show he was remorseful (counselling, voluntary advocacy against that kind of violence, etc) but I think he falls into the Petry tier so I'd prefer to just do that in trade