No it's not, putting Nylander with two guys who will do nothing all game is not a win-win. They just need to shut down Nylander and the whole line is shut down, The same with the Marner and Tavares line, they just need to shut down Marner and the line is useless.
No, Nylander can elevate the play of his linemates. Robertson can put the puck in the net, although he’s probably the one who will come out (personally I would take Jarnkrok out instead). If he plays, I expect to see the Nylander who started the season on fire. As for the Marner line, if they can at least come out even (and with how much money is tied up in Marner and Tavares, they should always come out ahead), I could live with that.
Another thing, how well has having two stacked lines in the playoffs worked so far? The Leafs need 3 lines capable of scoring to win in the playoffs, and spreading out the talent is the best way of accomplishing that.