I don't see a reason to have a mass of water in a nice insulated cooker to keep the temps down.
An air leak is an air leak. You should be able to limit the oxygen enough to control temps. Just like a UDS, or a WSM or BGE for that matter, with no water. I'm confused, and would really like to see one of these setups in person, or at least see pics of how the draft controller connects to the intake, etc..
Something is out of whack, and I refuse to think a mass of water is gonna fix the problem.
For the people who are using these, have you tried to run them sans draft controller? I haven't seen an answer to this question yet. Ya should be able to control air via the intake manually.