I just tried to get a 4 Star + HP% gauntlet for the hard/brutal mission and after 50 attempts I have gotten only 4 4 Stars.  What is the drop rate?  I know most are skipping this until they get to brutal so they have a better chance at getting a 4-5 Star with a specific %, but how difficult did the devs want this to be?  Right now it looks like its a pretty rare drop.  I don't even need the damn thing, but my missions have stagnated now.