I'm thinking this will be a more where you are rewarded every few waves / after boss waves with engrams, shaders, ships, glimmer, chance at exotics, etc. I think this mode is meant to be a repeatable time killer with a chance at loot like roc strike farming. Once a week loot drops aren't very sustaining for the game to last. Raids work in wow when they aren't the only thing to do, but in destiny, people with 3 32s and several hundred hours have played everything to death, and one more weekly addition isn't enough for them. As more people complete their gear collections, the addiction to the chase ends and they need to actually have fun to keep playing.