I have the same problem with mine, I have two sub tank minis both using the rebuild able section one with Heisenberg at 50/50 which is fine and the other snake oil at80% vg and am constantly changing the wick due to dry hits, in the end I tried a lemo 2 with the standard coil and fresh organic ... cotton, and two weeks in not one dry hit, the flavour and vapour are no different to when I first got it, have taken it up to 45 watts but sweet spot is 22-25 watts,
Anything over 15 watts on the mini results in dry hits.
(All with 0.5-0.8 ohm coils)