Cuomo, Schumer, and company will easily coat-tail Owen's re-election.
Yeah, that's the part of the equation that everyone seems to be missing. The Democratic ticket will be headed by Cuomo/Schumer/Gillibrand, while the Republicans have Lazio/nobody/nobody. A 65-70% steamrolling a la Spitzer/Clinton in 2006 would mean positive coattails for the Dems in every district except maybe NY-26.
You're assuming that Democrats will come out to vote in races that are expected to be blowouts. They didn't this cycle - and the Westchester and (likely) Nassau County Executives paid the price for that. You're also assuming Cuomo will run.