It would be so easy to implement and would be something that could be a challenge depending on what the modifiers are. Lets be honest, most of the 315-320 players can do the raid in their sleep with a competent fireteam. Adding this might spice things up a bit and add another way people could get that last item they need to reach 320.
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That's how the nightfall should be actually :( It's sad that It's not there anymore, and it now drops (mostly) useless stuff. Rep is good to have now though, but with no exp bonus is like meh.