Wait, who are these much better players in attack De Bruyne is playing with? Schurrle doesn't count since he joined in January and he was playing just as good even before he joined Wolfsburg. Are we really going to pretend Caligiuri, Bendtner, Dost, Olic, Perisic, Vierinha and Aaron Hunt are exceptional players? Their team is basically KDB and even WOB supporters won't pretend otherwise, virtually everything goes through him. He makes his teammates better.
Saying De Bruyne lacks pace smacks of complete and utter ignorance. He's extremely quick, arguably faster than Firmino.
12/13 De Bruyne 10 goals, 9 assists for Bremen Firmino 5 goals, 2 assists
13/14 De Bruyne 3 goals, 6 assists in half a season, Firmino 16 goals, 11 assists
14/15 De Bruyne 8 goals, 15 (!!!!) assists, Firmino 6 goals, 7 assists
As you can see it's not really much of a contest.