You don't.
Read Carefully: [url]http://www.bungie.net/en/View/bungie/eula[/url]
You are LICENSING the rights to play Destiny.
Any content that may have been on the Disc at time of purchase is not yours it belongs to Bungie and Activision.
Therefore you were never cheated out of any content as it was not yours.
If this is unacceptable to you there was a 30 day refund policy granted to you in the terms & conditions that you probably didn't read. If it has been more than 30 days you have no one to blame but yourself.
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For a year, they showed us a game that they told us was Destiny. The game they released was factually, substantially different from what they had previously shown. Yes, there was, no doubt, a disclaimer that said "subject to change." However, do you suppose Activision knew that the things they showed pre-release would influence sales? Do you think they knew that the things they cut from the game after showing them as content would matter to consumers? In your opinion, do you think that a company which makes use of disclaimers and "fine print" to legally, if not ethically, substantially lessen release content versus pre-release demos and previews is deserving of your future spending?