That 3rd line might turn out, in '19-'20, to be one of the best and more effective 3rd line in the league. McCann and Malgin made great progress, last season, and they'll each have a great one in '18-'19 & we all know that Tipett is going to be a star. I think he stays in the OHL in '18-'19 and makes his debut in '19-'20 on that third line.
The first two lines are very strong and well balanced. They will score a lot of goals.
That defense is getting more and more experience and, with the addition of Faulk, at the and of the season, might be in the 5 best in the NHL.
The only weakness I see is Reimer...and it's a big one! It's totally possible that he finally makes that next step to become a real solid and consistant starter...but that's not that likely. They'll have to address the position sooner or later.
All in all, they'll have a strong 2018-2019 season, making the playoffs as an 8h seed. They'll come back stronger in 2019-2020 and, I think, will be considered contenders then.