That is common with the kanger coils. There are some things you can do to mitigate the leakage:
1: If you take too hard of a drag, you can pull more juice into the coil than the coil can vapourize. To help with this, do the following, turn up the voltage so that the coil will heat up faster and hotter. I usually set mine to around 4.1-4.3 volts depending on the juice and flavour of the juice I am vaping. It is a balance game. If your coil is flooded, remove it and blow into the stove-pipe at the top to push out the juice inside. Make sure you have a kleenex or paper towel to catch the juice. Once purged, replace it into the tank and it should be good to go again. If it floods immediately again, chances are there is not enough silica wicks at the top of the coil and too much juice is getting in. That coil will need to be replaced. I wouldn't throw it out though....see below.
2. Stock coils have three pieces of silica threads used for wicking. Some people will replace those wicks with a piece of organic cotton. Do not use too thick of a piece though, too much will block juice flow. The top stove pipe can be removed easily from the coil.
3. When you get more comfortable with your gear and builds, you can always rebuild the coil with kanthal wire and organic cotton balls. After a month of using stock coils, I saw a vid (rip trippers on youtube) that showed how to recoil and rewick a protank coil. Very easy to do once you have the tools. It takes some trial and error, but once you have it figured out, there is no going back to stock coils. I have not purchased new coils for my protank 2 since november 2013. My coils rarely flood. I have burned the wicks (cotton) a few times from not properly priming the coil (tastes horrible BTW). I usually wick 10 coils at a time. Once I get down to 1 replacement coil, I will rewick the used ones. This takes about 20 minutes and I usually do it while im watchin TV.
I will also add, that the coils I rebuild with cotton last anywhere from a day to 4 days. The variable is how much I vape on the coil. I tend to chain vape, so for me, I naturally go through coils faster than a person who only has a few drags every hour or so.
4. Youtube is a great asset for research. Sometimes just reading how to do something is not enough. Seeing how an experienced person performs a specific task greatly speeds up the learning the process.
Do not give up on the protank. It is a good piece of kit, and its in my daily rotation. It can be finicky and frustrating at times, but once you understand how it works, it is rather reliable. There are those that will say its junk, but I strongly disagree. You have to understand your equipment and maintain it in order for it to work properly.