in general im of the belief that pure talent is more important than 'depth' or even-ness of the lines. a good team will have a clear top line, a second line that is practically a first line on an average team, a third line that has the possession metrics of a decent second line and a 4th line that acts like a third line. there is surplus value on each line and at worst should be even up vs every opponent even a good one.
if you run out 4 lines that are roughly even, to get that same value youd need all 4 of them to be at least a solid second line as 1/4 of the lines will lose to the other top line, 2/4 will be even-ish up and 1/4 will only dominate the opposing 4th line...if they even play. this even lines team can beat up on weaker teams, but should lose to good teams.
it is extremely difficult to sustain all 4 lines playing at a second line pace for an extended period of time. in addition, role players typically do not play as well in the road for various reasons as they need at least some momentum going their way to be productive. players of top line ilk should be able to score regardless of the game situation, especially so when they're able to score against the flow of the game. these teams will win games they didnt 'deserve' to win which youll need a few times during the season including the playoffs.
i predicted in one of the threads at the beginning of the season that the 4 North playoff teams will be Toronto, Winnipeg, Edmonton and Vancouver as they have the top-end part of their lineup figured out and just need to work out their depth. I believed Montreal would miss. Vancouver had too many injuries so Montreal is currently in that spot right now but man they dont look good cause they dont know who to count on in crunch time other than probably Toffoli.