What is up with the rumble boxes especially the silver and black rumble boxes.  As of the past 6 days I've opened about 20 (if not more)silver rumble boxes plus 1 black rumble box and, not once have I got an active skill for my level 7 heroes nor did I get a new hero. It'd be great if this issue was addressed and fixed by improving the rate of getting a hero or skill after opening a certain amount of rumble boxes per day like if you open 2 silver boxes one day, opening a third silver box on that same day gets you either a hero or an active skill.