The size of the orbs depends on how you charged your super. Its to stop people stacking supers especially regarding Crucible. If you charged your super by picking up other people's orb then the orbs your super drops will be smaller and carry less charge. Don't believe me? Take a friend or two into patrol when the 'enemy moves against each other' and spam supers, pick up each others orb and carry on. You'll notice the orbs get smaller and smaller the more you carry on doing it. It has nothing to do with the amount of Intellect you have.