Backtracking much?
Goul was heads and shoulders above Leier, because while neither can make plays (Leier 1-3 isn't much better than Goul's probable 0-0), Goul is just as fast and he hits people from the moment he hit the ice. Not just the goal by Laughton, but in the 3rd period, he hits the D-man who ices the puck out of panic when he sees Goul gunning for him.
Hitting intimidates. Now you're not going to have a team of guys who hit unless you can clone Gordie Howe, but you want a few of these guys, the way Gudas makes people slow up at the blue line, Goul makes people hurry in their own D-zone and make mistakes.
This is why I want NAK over Leier, why I look forward to Ratcliffe when he grows up, etc.
And you need defensemen to clear the crease, early in the game St Louis D-men knocked down Filppula and literally shoved Simmonds all the way across the crease, eliminating screens. Size matters, put Allison in the crease and he'll be tougher to move.
Hitting and size aren't the be all and end all, but they make a difference. And their absence is obvious.