I have never been able to consistently tune a guitar using harmonics. It was always a fun trick when I was first learning to play, but it was never quite right and now that I'm older it is far more difficult to hear subtle differences between harmonics.
It's been quite a while since I tuned a guitar this way, but isn't the trick with using harmonics that you listen for clearly audible "beats" when it gets in the ballpark? Once there are no more audible"beats" you're in tune.
Hearing loss has no impact on this - unless it's really, really bad, of course.
That would definitely get you close, but the range that the "beats" are not audible is a wide range and in my experience hearing loss had affected my ability to detect their absence.
