I grew several specimens of William Baffin for about ten years. I raved about them for the first few years, and then they disappointed me. They started to decline, with less and less bloom, and even got diseased. It may not have been blackspot, but it was a leaf fungus of some sort. I tried rejuvenation pruning, which is quite a task with his rose - the canes are like tree trunks. Nothing worked, so I cut them back to the ground and replaced them with other varieties. Suckers like crazy, even years after I chopped them down.