FPV is a very useful aid, especially if the failure means you have lost AP+FD. It gives you a lot of info with respect to track as well as vertical profile.
One caution is if the failure concerns pitot/static malfunction. From memory I think it's specifically the static side of things. Take a look at "unreliable airspeed" there is a line in there which says something along the lines of "if altimetry is affected FPV may be unreliable."
Hope this helps.
A4