Doug,
I have never had a problem with Hagen powerheads. Used them for more years than I care to remember. Never has one failed me. I would use no other kind myself. I,m going to look at the shafts, as I no not of which you speak.
On the skimmerless issue. I have tried many ways but always end up going back to my skimmers. Even with the use of my multi-billion $$$$$$ scrubber.
Thinking of giving it another try on my new 75g sps cube. Currently is running a large beckett, direct from the tank. My turf scrubber was rated for 250g, but it had trouble filtering my 225g. Perhaps I fed to much. Anyhow, one would think it would do well on the 75, even if its all sps.
Seems aquarists now feed their sps corals, so perhaps a skimmerless but turf scrubbed tank would also do well for them. I plan on using the flow from my stream pumps to keep the crap in suspension, until taken out by powerfilters.