The leaking I can say is all in the design yes. Taste and such, then several things come into play. Type of coil (vertical, micro, nano, standard wrap), type of wick (silica, ekowool, cotton yarn, cotton ball, ceramic, stainless cable or mesh), resistance of coil, voltage or wattage output, thickness of your juice. Stock coil we can easily say we are dealing with a standard wrapped coil around a main silica wick and a couple small floating wicks, resistance (1.5, 1.8, 2.2, 2.5, 3.0??). Now, question is how thick is your juice you are vaping (70PG/30VG or higher PG, 60PG/40VG, 50/50, 40/60, 30/70, 20/80 or thicker)?
A stock BCC head should handle upto a 50/50 blend if the VG is thin, start getting thicker, those floating wicks mentioned need removing 1 to test, if still burning, 2nd floater needs removal.
BCC tanks have a slight learning curve as so many factors play into their performance, but once dialed in to match you vaping habits, they are one of the best performing tanks on the market. External Temperature, air flow holes, coil, voltage/wattage applied to them, liquid thickness, coil and wick type all play subtle to major roles as heat, gravity, and pressure all affect the device. Many get into modifying and re-building them like myself to predict so much about how the tank should perform, especially on a variable voltage or variable wattage device.