If they are .. are they necessary? (during warp)
There is a reference to "Main Shields" and "Navigation Shields" in TNG, (Outrageous Okona?)
I really wish they had stuck with Deflector and Shields as being two separate systems. They started doing that in TMP, dabbled with it in TWOK, and even brought it up again in early TNG.
I still choose to take the term "Deflector Shields" as describing two different systems that work together in tandem. I've always maintained that the "bubble" effect we sometimes see are the deflectors at work, while the skin tight fields are the shields.
On a separate note, I really think the introduction of point defense systems in the new 'Star Trek' (what three digit short form are we using for that?)...I've mentally retconned it into all previous trek.