I've already responded to the playoffs bit. It doesn't hold up to scrutiny. It's the ultimate small sample and even in this specific example, hits some problematic stumbling blocks (Drai got half his points in two games; was invisible for much of Sharks series and Game 7 vs the Ducks).
More concerning are the 82 games he played before that. Elite with McDavid, average 2C without.
He had the flu bug, like I said. It even looked like Connor and Maroon played with injuries. Maroon, especially in his ribs. Whether you disagree about the playoffs not holding up to scrutiny, its still a factor for Draisait's camp regardless. Then the signings of players like Kuznetsov was also another factor for his camp.
And like I previously mentioned, the real questions will remain for Drai next season aka driving his own line with two specific wingers with success.