In Enterprise Earth ships don't have shields and travel at up to Warp 5.x.
A navigational defector wouldn't be considered shields as it would not stand up to direct fire.
I am modifiying my opinion on how warp works, after I posted I refined it down.
You do move when warping so a navigational deflector would be needed. Here is why.
The warp bubble is nothing more the actually compressing space in front of the ship and expanding it behind, but it doesn't really move the ship (acts as a movement multiplier as a small move in compressed space equals a large move in normal space). The impulse engine then moves the ship forward at speeds up to light speed, but because of the compressed space it becomes alot faster.
Imagine steping forward into compressed space (say compressed by times ten), one step forward and you would move the same as if you stepped ten. To an external observer this should look like the warp jump when a ship takes off (the stretch of the shape) If you were moving a longer distance you would just stretch and disappear. Seems logical anough. So in my opinion you need deflectors at warp speed.
Oh, as side note, you wouldn't take anything with you as only you is moving not the whole bubble of space, the bubble effect moves forward, space compresses ahead of you and decompresses behind as you move.