I thought the mileage was on the low side myself especially since I got almost 3000 on the chain. I'm on the anal side when it comes to maintenance so the drive chain is clean and lubed. I don't ride this bike in crappy weather so really it should last longer.
I put the new cassette on so I'll give it a go tomorrow and see if that takes care of it. I have a feeling it's something else but we shall see.