The Nats' average of 6.13 innings per start out of their starters is the best in the majors right now; they and SF are the only teams averaging six innings per start (and what good has it done the Giants?). More than half the teams in baseball fall somewhere between 5.5 and 6.0 innings average per start, with the Rockies ranked 8th overall (5th in the NL) at 5.6 innings per start. So while it's obviously good to teach young pitchers to pitch more economically and get deeper into games, the Rockies are nowhere near the point where this has been a major issue for them, in fact they're better than most right now. Everybody struggles to get through six innings these days, which is why bullpens are such a huge component in today's game. 

Another bullpen arm to replace Ottavino or Dunn would be a huge help, it would allow everybody below them in the bullpen pecking order to slide down a spot and would push somebody like Lyles or Oberg out of the 'pen entirely.