The real reason that black heart was needed to be destroyed is because destiny has no heart. [spoiler] As we awoke from slumber the little ghost told that "There will be alot you don't understand" and as time progressed and now at the conclusion of 'destiny's initial' story..there wasn't even a single occurrence where the players (us) were told besides "I wish i could tell you but.." . The fact remains that we weren't told anything within the game (besides the intro of course)..so its best to assume that destiny is heartless now considering that we actually destroyed its heart. [/spoiler]