I'm going to agree that it's probably the wicking at issue, and if you've used too much cotton (which I did a lot of to start, and I got leaking) you may need to go thinner AND shorter. I know this doesn't make much sense, but you really need your wick to be exactly right, in order to avoid dry hits AND leaking. I'd try using what seems like "not enough" and "too short" cotton and make sure you thin out the tails. It took me a long time to master this. I'm not even going to get into coiling, but, as usual, my problems with wicking were "too much" not "not enough." I was really surprised at the size and shape of the wick that I needed actually, I was pretty sure things weren't going to work out, but they did.
Best of luck,
Anna