Not so in my case. For the past 5 years or so I have had ALL working files on a NAS and only system files on the local devices (on SSDs). Latency hasn't been a problem for low usage stuff like spreadsheets, word documents, pictures etc, even CD/movie ripping has been OK over the LAN. Until I bought the MBA, access has always been via a Gbit LAN - now I use WiFi for the MBA and the LAN for the other devices - still without a latency problem.
So again, it depends on your usage profile.
Depends also on the reliability and load on your network. In an environment with several Apple TVs and a couple users, some wireless thrown in, real time work using files on the NAS screeches to a halt... and then there is quite a jump in risk of file corruption.
In my experience over that last 10 years, but more so recently, for better reliability and performance, local DAS is the way to go.
Now at the office, where there are no casual users, everyone avoids working real time off the NAS if they can. There is no wireless there and the equipment is top notch.
It seems like your application is more of a single user, so there are many fewer NAS issues.
But again, depends on what you are using the storage for.