2016 Specialized DSW Elite worth $400?

I think the price is on the high end but in the right range. You may be able to negotiate down on the reasoning that it needs a pretty thourough service.

I like this model still a nice aluminium frame carbon fork design. The tiagra 2×10 drivetrain is solid not flashy but it is nice to be compatible with all other Shimano 10 speed stuff. 

It looks like it has barely ever been ridden. That is overall a good thing but it’s not good for it to have sat with flat tires and can’t trust that all the grease and lube hasn’t dried out. Plan for a full service