$500 for that bike in 2013 is a good deal. I am sorry to hear that you missed it. Just know that prices will start to drop as the new models come out in the fall.
The Diamondback frame isn't bad per say, just slightly more material then comparable makes (from my observation: the tubing sounds like thicker gauge, and there is less forming or butting, so overall it has more metal.
I am curious how you came to that conclusion. Both the DB Pod 3 and Trek 2.1 weigh around the same (20.5 lbs). Both are similarly equipped with 105s. If it is a heavier frame than I am wrong, but it looks to be about the same as others.