I don't think anyone really cares too much about weekly heroic matchmaking. We mostly wanted nightfall matchmaking regardless of some of the bad traits that could come along with it. So, why only weekly heroic?
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Trolls need to stay out of Nightfall. Imagine a Nightfall and you are about to win and and a troll causes a wipe just for "fun". AFKers are a plague - they must learn that gear must be earned. Nightfalls require teamwork and mics to finish it. Matchmaking is just a hindrance waiting to happen in Nightfalls, and Raids for that matter too.