I originally thought the protank 2 was using less juice than my old Nova; turns out that it the optical illusion of the tank being shaped and sized differently. If I use a stock head, the consumption is moderate. If I put a 1 ohm nanocoil or a 1.6 ohm microcoil in it with a cotton wick, it will chug like a frat boy during rush week. Literally filling it up 2-4 times a day. I actually wonder if this tank wastes juice by allowing a ton of heat top build in the coil chamber, and then allowing juice to come in and get evaporated after the drag is done, due to said heat.
As to the leaking issues, I think the phase of the moon has about as much to do with it as anything else. I have had a stock head randomly start leaking for no reason, and I have had a beat-to-hell rebuild hold every drop in until the tank got under 10%, and vice versa. They are fiddly devices for a fill and go tank, it's like using a Mac: you don't make the tank do things, you more like trick it into doing what you want it to do. They are not bad devices, just each one, and indeed each head, has a bit of a personality to it, and you have to learn to work around it, unfortunately.