McDavid's on-ice results were better away from Barrie than with him. Barrie away from McDavid was a disaster.
Who cares? Seriously, why should I care if he can put up points if those points don't actually translate to wins because the rest of the roster is shit?
It's not about Bouchard replicating that level of production, it's about allocating scare resources (cap and roster space) to areas where they'll have the greatest impact and as long as Bouchard or Bear doesn't absolutely tank the performance of the top unit (which seems unlikely), you're better off spending money elsewhere instead of paying a premium for a handful of extra points for a line that is already perfectly capable of outscoring the other team.