I guess I am just lucky. I have various sub ohm tanks that use pre built coils and I have never experienced any leaking of significance in any of them.
I have 5 packs left of 10 packs I purchased of TFV4 quad coils when it was released that cost me ~$30 each and I haven't used that tank in months.
Having extras is just part of the game I guess. I understand your point that these people claim their tanks don't work and I at least have functioning TFV4's if I ever wanted to go back. I wonder if those with leaking tanks have tried replacing their coil?
When I got my leaking tank replacing the coil was the first thing I did. Even with the new second coils it still leaked. Then I decided I had enough and sent back to the retailer.