Driving rain is not uncommon.

Less so than you might think.
If rain is accompanied by wind, which I'd say is the norm, then gutters
don't fully protect your walls.

The 'meter' and several firms said I did. Don't you read earlier posts?

What I'm saying, and I don't know how much clearer I can make it, is that,
if your plaster is in good nick, then you obviously don't have a damp
problem. Do *you* think you have a damp problem?

The pointing is what matters.

So we're relying on 1/4" of sand and cement, perched precariously on
(and invariably not bonded to) 100 year old bricks are we?

Yup. Or do you advocate 'treating' every Victorian - and later - brick
wall?
I try to alleviate damp to the best of my ability in the houses I'm
responsible for. In that respect I am able to monitor the success rate over
the long term and maybe my findings are of use to others, that's all.
Incidentally, I have a council wall half a mile long near here that was
re-pointed in just the way you suggested a couple of years back. At least
50% of the pointing is now missing. I tend to take notice of these things
and base my opinions on them rather than something I've read.