I've been using my Eleaf Melo tank all day (Eleaf version of the Atlantis one, basically the same tank with cheaper metal, they use the same exact coils,) and a .5 ohm coil with a 50/50 liquid on my VS DNA 30 all day and let it bounce around in my pocket and vape it and see how it vapes to see if I could give you some better advice and help....and here's the results of my one day study...
First off...always look for pocket lint in your drip tip before you vape
Secondly....I noticed as it bounced around in my pocket, sometimes it would be right side up, sometimes on it's side, sometimes upside down I noticed the following things... (also, I use my airflow all the way open,) A little juice seems to run down the center stem if it's not right side up all the time, that means the coil is oversaturated and when it runs back down or stays in the center shaft as I am about to vape it since it's on top of the coil assembly that liquid won't be fully vaporized and I get just a tiny bit of spitback for like a second and then it stops. 24.5 watts seemed to be about the sweet spot with the coil I currently have installed but since no two coils are exactly identical I may have to adjust it a bit for the next one. Also, I noticed after a couple drags and the coils wicking had dried out a bit that the spitting stopped until I bounced it around in my pocket again and let a little liquid run up the top of the coil and repeat the cycle again.
Try firing it for just a half a second before you start taking a drag off of it, i mean just a half second...just long enough for the coil to "spit" that little bit of juice on the top that didn't get hot enough to vaporize and resettle and then take your first drag. more than a second and you start to heat your coil up too much from lack of airflow and can singe it if you're not careful. Then try and take a second and third drag right after the first and see if the spitting problem goes away by the third drag...if it does your coil is simply just over saturated....basically it's the exact opposite of what happens to cause a dry hit or dry burn...your coil has more liquid than it can handle and you just have to vape it up and balance it out
I agree spitback can be annoying, but my tank spits so little when it does that I barely notice it except for maybe once a day when I get a big drop but any clearo can spit like that...it's not something exclusive to the Atlantis by any means. Just try that and see if it stops and then we can go from there to see if we can balance out your tank so it wicks right and keeps it from happening again.
Also, check your o-rings and your seals around your tank...sometimes an upside down or torn or lack of an oring or seal can cause the pressure in the tank to be out of balance and when heat is applied to the coil it creates a further imbalance flooding the coil...especially if you're going between drastic temperature changes from a well air conditioned inside place to a hot as hell outside place....sudden change in outer air pressure and temp can cause your tank to flood as well....
I know it's a lot to think of but I have a feeling your wicking issue is a combination of one or two of these things and can easily be fixed when we get to the bottom of it