The Leafs' biggest need, in my opinion, is the PK. 21st in the league with a 75.6 kill percentage isn't good enough. While I personally feel that Hakstol and Andersen are the root of the problem, those issues are more likely to be resolved in the offseason. From the numbers I've seen, Pitlick seems like a good option on the PK and his price tag should be on the smaller size. Granlund has also played a bit of PK this season, and the Leafs are heavily connected with him. I think the most the Leafs would be willing to pay for Granlund is Kerfoot and a first, but they will probably get him for cheaper. I'm less sure of Pitlick's trade value, but I am certain he's not untouchable. It really depends on whether the Coyotes will be sellers at the deadline. I would have also liked to have added Khaira, but I'm unsure if Edmonton would be willing to sell to a divisional rival.
In terms of the lineup, I think that Thornton will eventually settle into the 3rd C role as the season progresses. I don't think that having Jumbo on the 1st line heading into the playoffs is a recipe for success. Simmonds looked good on the 2nd line before he got hurt, so I'd give him the chance to keep that spot once he's back. If he falters, then Nylander should be put on his off wing and Granlund should be promoted to the 2nd line. In the interim though, I would like to see Tavares and Marner reunited. Matthews needs a second shooter on his line until his wrist is healed, and Nylander's shot is superior to Marner's. Hopefully Marner sparks Tavares too and helps him drive that line.