I have done tens of thousands of miles on the 2014on model RT 1200. Have tried various Metzeler, Michelin, Avon and Conti tyres on them.
Whilst I would not rate the PR4 as badly as you do (can it be a duff rear i wonder?), I also think they are the worst choice for that bike. And the worst lasting.
My best option was (and still is on the K1600) the Metzeler Roadtech or Tourtech. Avon Storm was a good second choice, but I m not sure they are produced any longer....
In fact, i am such a Metzeler convert, they are now an automatic choice for most of my bikes. I find the Roadtech, the best tyre there is, albeit not the most durable either.