If having consistant problems with tire cupping, there's other problems. If a bad tire is ruled out...and I think you can do that if you've put 2 or 3 tires on the bike and they all do it..., and you keep the tire properly inflated at all times, and properly balanced when installed, then there's one thing looking you in the face: Suspension.
I worked with tires for several years in my younger days, and would see cupping on car tires. MANY times, the shocks on those vehicles would be completely shot. While there are definitely cases where the tire is defective, it's more often due to other causes, and poor suspension is more often than not, overlooked. I have pulled many a shock off a car that were so worn out you could push/pull them in and out like a trombone, so the only thing working was whatever kind of spring was sitting over that tire. Springs do not have damping characteristics. And lack of damping causes tire cupping.
The stock rear shocks on a HD are not worth a chit in the first place. Put 10K on them and they are worse than chit. The front suspension is so pooly designed that it would likely amaze you if you could actually see how often the front tire is not in contact with the road surface due to poor damping characteristics inherent with a simple spring and POS valves.
To coin a phrase: "There's your problem right there, Vern"
As Jerry mentioned, there were known issues with the Dunflops in the '09 year models, but outside of that, there are other issues that need to be looked into.
Soap Box: Folks don't think a thing in the world about putting 3 or 4 thousand dollars into exhaust, cams, chrome, etc, etc, etc. That's all fine, and big HP/TQ numbers can be fun to chase. But most of those same people shudder at the thought of spending 2K or less putting something under the bike that will help it do things other than go fast in a straight line, and make the bike safer to actually ride. Of course, if all you've ever driven is the equivalent of a '68 Buick with worn out shocks, then you think all is well.