I don't believe anyone predicted that Montreal would have success with Gallagher, Danault and Tatar before the season started but that's what's happening. They are driving play with a 66.5% CF in 157 minutes of ice time. They have a GF% of 58% and their expected goals for is 60%.
I don't think they're overrated as much as they are just riding a hot streak. not saying they aren't good, but beyond Gallagher, the other two aren't as good as they've been playing.