cyberspacecat already mentioned a lot of the good aspects that came in this DLC drop, but there's also a bunch of changes that have really improved the game between Curse of Osiris and Warmind. I'd recommend even just glancing at the first image in a couple of the Development Roadmaps over at Bungie.net. For example: almost all of the underwhelming Exotic weapons got additions or changes made to them that make them really fun to use now, and heroic strikes have become a lot more difficult with additional rotating mechanics layered on top that differentiate them from standard strikes or nightfalls.
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