Bungie Twitter already posted the link but the way to fix the matchmaking it's pretty simple, be patient. Now that sounds like a dumb thing to say but hear me out. As you go into the blind well hallway stop when you get to the large curved steps that go left and right. Go up the right steps crouching and hugging the right wall all the way until you hit the next split hallway. Keep following the right wall all the way until you hit the blind well instance. ( I tested this sprinting, walking, and crouching when you pass beyond the stairs and the slower you went the better the matchmaking worked it seemed.) Tested the theory solo and with teammates worked everytime. It's a weird temporary fix but since it works I won't complain. Edit: You aren't guaranteed to find people this is just the best solution for it. Running in and out will not re-instance your matchmaking but fast travelling back to the main area will.
when all else fails, fire up a single, by the end you'll have enough for a three stack to make heroic, do that twice an done. Though I will say it was tough to find one already going. The crouching tiger bit usually works but not this week it seems.