Agreeing with what others have said about your coil. 28g is much too thick for an outter clapton wrap.
If you don't have any thinner wire to try, maybe try making a standard coil, and see if that's any better. If so, you know your problem for sure.
If you wicked this the way Matt did, it should preform well. I'm using a 0.3 ohm triple-core fused clapton (40g outter wrap) and it works flawlessly wicked the way Matt advised.
If you're still having wicking issues after switching to a standard coil, you'll know it's your wicking technique. This RTA doesn't require a lot of cotton at all, just remember that.