I haven't been commenting on here lately. What John said, plus I agree that cleaning your duct work would really not make all that much difference in drying accuracy. It would probably just slow everything down a lot. It's always good to keep your duct work clean and as short as possible. Few turns is best. Common sense things really. Low air flow would increase drying time, can cause your dryer to get hotter than it might normally get and increase your energy bill. Overloading your dryer will affect it's drying accuracy.
As far as HOH dryers, I have found them to be spot on when loaded properly. I also added an adjustable cool down thermostat and set it at about 90 degrees (if I recall correctly). It gives the dryer about 10 minutes cool down, +/- a minute. This made all the difference in the world in the accuracy of that dryer. Plus, the clothes were fluffier and more lint free at the end.
From what I have been told gas HOH dryers work OK, everything else being equal, as long as the front seal holds up. When it starts to deteriorate, so does performance. The front seal is NLA. If I were ever presented with a gas HOH dryer seal in a state of disrepair and I had the materials, I might attempt to duplicate it. So far that occasion hasn't arisen.
I hope this helps.
B.