It appears to me as if something is wrong with the fluff side of your attempts.. too much I guess.. did you try to tune that too?
I have found that the amount of Fluff can hugely influence how the atty (Heron) wicks. For a while there I was getting one of two things; either dry hits, or I was having to fill the Heron way too often. In both cases it was due to using WAY too much Fluff (it was not releasing the juice like it was supposed to). I was wrapping it much too tightly around the bell, and was using upwards of 4-5"!! Since cutting back on the amount of fluff (more like 2-2.5" now) I get MUCH better wicking and the vape quality from the Heron has gotten a LOT more enjoyable!
You want it loosely wrapped around the bell, and you'll want to make sure that it touches the tank walls. What I do is then go in with a pair of tweezers and "spin" the fluff in the opposite direction that I wrapped it....this helps to spread out the fluff evenly....maybe try a build with a bit less fluff and see what happens?