You can get treasure keys from the two side chests after PoE, and you can do level 28 PoE as many times as you want. In my opinion playing PoE and leveling up guns and House of Judgement reputation as well as just the fun aspect of it is a lot more fun way to farm than waiting on wolf packs for 10 minutes at a time. It takes roughly the same amount of time except there are two chests at the end and not just one. Please stop hating on Destiny that you have to go farm keys on patrol, you don't. Just play PoE. Edit: This post was for people who are saying they hate destiny because it's making them wait around to farm keys. I am NOT telling people what to do, just giving a heads up on the options for getting keys.