Of course they'll scapegoat used games, they obviously made a "good" product that is completely "worth" $60. >_>
I just hate how they never quite understand that MAYBE their game isn't up to par and didn't meet expectations because it either didn't have enough content or just wasn't good to begin with. Used games have always been there and they're nothing but beneficial to sales, because used sales usually lead those players to buy the sequel on day 1. If they don't, they never had the money to buy it new in the first place. So I don't see their point in attacking them.
Now as for the various forms of DLC, it's hard to say. Costs of development have basically skyrocketed since the Playstation era. Ever since games like FF7 and Metal Gear Solid came along, it's been a game of catch up for many developers. The need for CD quality orchestral soundtracks, a decent and varied voice cast, bleeding edge graphics, cutting edge motion capture technology and an ever growing team of developers/actors/musicians/coffee makers needed to make this game a reality. Games are now rivaling films on inflated budgets with games like Mass Effect 3 and RE6 having millions upon millions put into the game.
Honestly, I'm not sure if we'll ever know that the DLC is necessary to make ends meet. Seeing how nowadays a game that mediocre sales could be the deathbed for their entire development studio. Personally, I'd rather see these insanely overproduced games go away. Reason people keep complaining about how JRPGs are dead is because they hightailed it to portables to avoid their developers get crushed by high development costs.
I'd rather that publishers instead gave first buyer incentives like smaller publishers like Atlus do to sell their games instead. I think it's a win-win situation and I like how Ubisoft has been doing that with their pre-orders (wish they'd back off the DRM bullshit) Instead of penalizing people that buy it used.