I'm actually not a huge fan of Occam's Razor- I might do a full post on it soon, actually.
As for the comets- there are a lot of problems with the idea. It would create dune-like formations of dolostone, which aren't exactly common. It would also distribute the dolomite much more widely across the Earth than actually would seem to be the case- and since we're not finding dolomite dust contamination in nearly the amount of contemporary sedimentary rocks to the dolostone. Plus, though comets do contain carbonates in their tails, we don't have evidence that they're present in enough quantities to pull this one off.
I'd be interested in reading that.
Actually went ahead and posted it already!