I've always been rather fond of the aquaclear HOBs, and thought they were a pretty good filter for the money spent. I've been out of the hobby for a bit, but I'm pretty sure I got at least a couple-few years continuous use out of mine without trouble, and with minimal maintenance. Are you using a prefilter? I've almost always used prefilters on my tanks when I've had a HOB or a cannister. Mostly for the welfare of the critters, but even a tiny snail can cause some damage knocking about the impeller chamber.
As to the gas exchange bit, that's only a real concern if you are injecting CO2 (I'm pretty sure one of the defining aspects of 'low-tech' is a lack of CO2 injection). Any sort of surface movement/turbulence/etc. will primarily work towards bringing the ratio of dissolved gasses in the water in line with what is present in the atmosphere. (something like ~79-80%N2, ~19-20%O2, ~1-2% of Argon, and then traces of everything else) So if you are injecting CO2 into your tank, then gas exchange will reduce it. on the other hand, it will also bring in O2, which is necessary both for your critters, and for the biofilter.