I actually spot before developing the image.... (just kidding)
I also spot first. If I mess it up, I'm not wasting an expensive backing paper. Heat does not affect spotting dyes. Also, smaller size of paper helps me handle it better. I wear a white dust free cotton gloves while doing this, so that I don't contaminate the print. Works for me.
I spot (when I absolutely have to) before dry mounting. If I screw up the print it's easy enough to do another one, but if it's mounted then I'm not only out a print but I've pretty much hosed a mat board too.
Since I started using a glass carrier (thanks to Mr. Carnie ) I'm finding that spotting is pretty much a necessity no matter how careful I am. I think your suggestions are very reasonable (i.e., spotting before mounting) for all the reasons stated. Off to learn how to do it well.....