Neither Pyrocat HD or PMK are fine-grained developers. They're less grainy than other pyro developers, but that's not saying much. (I'm using Pyrocat HD for my medium and large format negatives.) Morever, with PMK you probably have a problem with low contrast highlights on HIE, especially on VC paper. Xtol, ceterus paribus, will be less grainy, and it works well with HIE. (I've used this combo extensively.) I've never tried a real fine grained developer, such as microdol -x with HIE, but it might be worth a try. (You'll probably lose about 1 stop of speed compared to Xtol.)