I agree, broken. I went into the K1 Revelation Lost Sector on the Moon and used melee on everything maintaining devour for at least 3 streaks and got no progress. I let myself get surrounded and still couldn't kill them fast enough to get any progress. Progress bars should show x/10/x2 so you can see if it is working. These bounties are the most frustrating since they are kill x number in a row to make progress and no idea if it is working until you try everything you know to see if it will work.