I've had two full-blown cases of scald this year and no rot and my ground isn't any drier than anyone elses.
I don't routineley trim feet and I think this helps, I also cull for feet, after getting the sheep better. I have never had one that didn't get better after trimming and then spraying with alamycin (mostly use the purple spray and that works fine in most cases, alamycin in persistant ones).
However, I don't turn them over all the time to see if there is any developing - I catch and treat limpers. I reason that if they get rot/scald, and then get better with no adverse effects (ie limping) then so much the better.
If you brought your sheep in and they weren't limping etc, then I'd just leave them alone.