Isn't a bit apples and oranges to compare one person's xx/xx to another person's xx/xx? I would assume that there are variations between nic content and flavoring viscosities that would affect the overall viscosity and wicking characteristics. And that doesn't even account for undissolved solids.
Furthermore, I'm not sure I believe a "vapor lock" exists (though I did consider when I first bought my eRoll). I posit that different juices wick differently because of the above mentioned variables, and when wicks become clogged they filter the juice causing flavor change and a hard draw. When the draw becomes to firm, a vacuum builds causing juice to be sucked either through the wick or where the atty meets the spike, thereby flooding the atty and causing gurgling (when juice gets trapped between the cone and tank, and even inside the tank). I believe leaking is caused by capillary action, and the rate of leakage is affected by juice viscosity and slight variations in the manufacture of the attys, tanks, and cones, not because there was a lack of vacuum in the tank or some kind of vapor lock. If my eRoll has such a hard time holding a thick liquid, I find it hard to believe any part could ever be airtight.