For what it is worth-
My areas where rabbits ate the fans down to the rhizomes do not correlate with those where I had rot or other problems, so I don't think rabbit pellets are involved. Cutting the leaves has been an experiment: I left some uncut and cut some. Those cut were easier to clean up in the spring giving less chance of insect infestation. Those uncut were a bit messier to clean up and held more moisture near the rhizomes in the "dried" leaves.
Last summer at a house a mile away the owner ran over the entire iris bed with his mower cutting everything to around 2" and did it shortly after the last blossom. His blooms were sparse this year.
