I don't think Heroes has any kind of bad luck protection on loot boxes. I don't think Diablo has anything for loot either? I could be wrong on those, but I'm pretty sure that it's just WoW (for legendaries and bonus rolls) and Hearthstone that have a system like t his.
Also, cosmetic items are Blizzard's sole revenue generator for Overwatch, so it would make sense for it to be different than Hearthstone or WoW that have expansions and/or subscriptions, because they don't want to make it too easy to get the things that fund the game.