IMO, I think the issues with the Leaf's D is overstated. They could use a true stud #1, I won't argue that, but any team would. I think as a grouping as a whole, their defence isn't THAT bad. There had been cup winners with weaker defence corps in the very recent past.
What did kill the Leafs last year was goaltending in the playoffs. I think Anderson is a great goalie, but he didn't play well at all... like Rinne and Hellebuyck who immediately come to mind. I think leadership was lacking last year as well, and this is where JT is going to help them tremendously.
Too early for me to conclude if they are top-5 contenders yet, so I agree with you there... I have them as fringe top-5; I have Winnipeg, Tampa, Washington, Boston, Pittsburgh firmly ahead of them.
I got Montreal behind Toronto... like about 20 teams back.
But hey! In 2-3 years, when the Leafs are in cap hell, we'll be running with Kotkaniemi, Suzuki, Poehking, Olafsson up the middle.