Are you inhaling directly into your lungs? That will increase the TH. Many, if not most inhale into their mouth first and hold it a sec, then inhale to the lungs.
It was just a thought, since you are already using a fairly high ratio of VG and a medium strengh juice at 18mg. I use 50/50 with 24mg and it does not seem like a lot of TH to me, even with the 1.7ohm Resurrector cartomizers.
Going to a 70vg/30pg ratio will lower the throat hit, but will also mask more of the flavor.