All the teams who won cups recently split up there top players.
Malkin/Crosby, Toews/Kane, Kopitar/Carter, Bergeron/Kreji,
Ror/Tarasenko.
Even OV and Backstrom were split when they won.
Drai and McD need to be split. Period.
Drai needs a player like we saw with Hall.
McD was playing just fine w/ RNH. I have no clue why that was changed,?
First thing you are arguing for splitting up players pre-emptively cause teams who won the cup did it, but the basic fact is we are a million miles away from winning a cup, much less be in the playoffs, if your argument was these teams did it and it led to better regular season success it would be of greater import. A lot of teams have had greater regular seasons largely off the back of one super line, it's in the playoffs where that dynamic often changes, when defensive structure and heavy game-planning upset what worked in the regular season.
The moral of the story is you need 2 good lines, so in the event one gets shut down the other can step up, it isn't you must keep the teams best players away from each other, you need a 2nd line you can count on, which fairly we are a long way off from having. Also in a lot of the examples you provided it was either two players who could independently drive their line and make the individuals around them better or two players who are natural C's through and through, to this point Drai is a winger more than he is a center.
Nit-picking I'd say Kuznetsov outplayed Backstrom in that years playoff push and it was actually OV and Kuznetsov who were the top 2 forwards, you could also make the same argument of it being ROR and Schwartz for the Blues, but that was close enough to argue either way.
If we could get back Hall or a Hall level player (and fit it in our budget) then great, but till then best make do with what we got. McDavid and Drai duo from a numbers perspective heavily outperformed the McDavid RNH duo last year, and RNH on our no mans land 2nd line outperformed Drai when he was put into that same situation. Things will likely change as next season progresses even great duos tend to get shuffled around at some point, but it seems likely that McDavid + Drai is something we are going to see a lot of going forward.