I have 2000 miles on my stock Diablo Rosso ll tires including 600 easy break-in miles. I would say I have maybe 1000 miles tops if that left. I have run 29-26 psi cold, currently at 26 psi front & rear cold and no matter what tire pressure I run even when the bike was stock the rear slides very easy especially when hot out significantly delaying throttle application exiting turns. That said they are certainly acceptable stock tires for the range of riders the bike was designed for so no complaints there. Also worth noting they're not the same tires as the off the shelf version.
What is the magic bullet to fix the loose rear end? The R6 shock in the rear made things better but still easy to get the rear to come unstuck. Is it a body position thing?
In the UK they come on Metzelers (owned by Pirelli now) M5 Sportecs. I think something Pirellis and Metzelers have in common is they are much better when they are new. In comparison to Michelin's Pilot Powers, the Pirellis are better new, lots of grips and feel but the Michelins wear better and feel better after 1000 miles or so. YMMMV.