No doubt those Coopers had some failures. I have the STT Pro, though. I am seeing no signs of issues like the earlier model tire. Have you any discussions that reference failures on the STT Pro specifically?
In all fairness, each of those threads you linked is from quite some time ago. For the most part, everything I've seen recently about Cooper has been nothing but praise.
People have issues with every single tire out there, including the ones that are well regarded (Duratrac sidewall issues, kO2 premature cracking/dry rotting, etc.) Personally I wouldn't write off an entire brand just because of a few threads from 5-10 years ago.
From what I've read, people do seem to be happier with the stt pro over previous tyres. A lot of people seem to still be wary of coopers because of the previous tyres having so many issues. I guess time will tell. Couple more threads on stt pro, with both positive and negative opinions
New Cooper STT Pro - Patrol 4x4 - Nissan Patrol Forum
Cooper STT pro or cepek extreme country? - ClassicBroncos.com Forums