I do very much believe the Nats are the team to beat in the division this season. Experienced talent has huge value over the long haul. And yes, as you mentioned, those returning from injury.
I think you are incorrect by leaving the Phillies unmentioned. Philly is only 3.5 out -- and has played a more difficult schedule since taking 2 of 3 from the Braves 3 weeks ago. ATL hasn't been overly impressive since ... lost a series at Boston (understandable) ... split a series at home against the Mets ... won a series at home against the Nats (impressive) ... lost a series to the lowly Padres ... lost a series to the Dodgers ... won a 2-game series against the Mets (again at home..okay). Unfortunately for the non-Braves fans, they continue with a relatively easy schedule ... next four ... Padres, @Jays, Orioles, Reds. At some point, they'll have a string of much more difficult opponents.
Again, compare that to Philly's schedule over that same stretch:
Most recent:
@Dodgers
@Giants
@Cubs
Brewers
Rockies
Next up:
@Brewers
Cardinals
@Nationals
Yankees
Nationals
The Braves had/will have 7 series with teams with worse records than any Philly has/will face over that same period. Over 162 games, it's bound to get more difficult and balance out. For now, the Braves are quite fortunate and need to keep winning before that schedule turns difficult. Philly, on the other hand, will see a much easier schedule in July. It's a long, long season.