You should expect more than 2000 miles out of a tire, I am not saying you are wrong about feeling that way and I personally don't use Dunlops for the reason that they simply don't last long enough for my riding style.
When installed on a bike that is well maintained (ie, tire pressures are checked regularly), there's no valid reason for a tire from an A List manufacturer that is marketed to touring bikes to be not only trashed after 3,000 miles, but to also have massive separation like so many folks have been posting about. I could see and maybe understand if this was from some low dollar off brand tire, or a high performance race tire, but on a touring tire from Dunlop? No, it's not acceptable.
I have friends who work in the automotive tire industry, and they won't use or recommend Dunlop either, for the same reasons - accelerated tread wear and separation. When I worked as a service adviser at a car repair facility, I saw the same thing with my own customers. I won't put another Dunlop on anything I drive or ride.