(FFT) Is it good practice to ignore each bin's phase when characterizing a signal
It depends,

sometimes phase matters and sometimes it doesn’t.

There is a paper by Oppenheim.


  Oppenheim, Alan V., and Jae S. Lim. "The importance of phase in
  signals." Proceedings of the IEEE 69.5 (1981): 529-541.


where an image is reconstructed with just phase and with just magnitude. The phase only image is nearly the same while amplitude alone is a mess.

For something like a stationary random noise, the signal model explicitly notes that the phase is random and is ignored.

There are probably a lot of cases where people ignore phase because it’s easier. Phase unwrapping can be difficult.  Interpretation can be difficult.

For cross correlation phase is very important.

It's never good practice to do things blindly.