The 2015 Nats' expectations could really be boiled down to 5 phrases. Max Scherzer is better than your #1. Jordan Zimmermann is better than your #2. Stephen Strasburg is better than your #3. Gio Gonzalez is better than your #4. Doug Fister is better than your #5.
Two 1-0 wins in a row is the stamp on a a great turn in the rotation by the Nats starters. Three dominant performances, one good but short one, and a decent 7 inning start. Maybe you wouldn't immediately match the pitcher to the performance but who cares? Each starter the Nats have is capable of having dominant performances.
Should you be concerned about the offense? Sure. This facsimile of Jayson Werth is hideous. Yunel Escobar, who was "so great" had one bad week and is back to being below average. Anthony Rendon may one day play back to back games. But with that starting staff (and a bullpen that hopefully finally realizes Blake Treinen is not your big pressure guy) you don't need a great offense. You don't even need a good offense. You can get away with an average offense and I think the Nats can easily hit that mark.
The important games aren't over with the Mets series though. Now the Nats have a homestand versus Miami and Atlanta. The Marlins are coming along. The Braves are trying to hang on. Both are a half game ahead of the Nats right now. A double series win would bring the Nats to .500, and likely put both of those squads in the rear-view. Any sort of middling performance or worse and the Nats are back playing catch-up to most of the NL East. Give enough teams, enough time and enough of a lead and someone will run away from you.