For a precision weapon like a scout or pulse rifle it's more difficult to consistently land headshots when you're holding the trigger down for full auto as opposed to aiming and then pressing the trigger when you're hovering over their head. That's why I feel like it's a wasted perk on those weapon types. Also, Destiny is very forgiving when it comes to hitting the trigger. Let's say a scout rifle fires once every 0.3 seconds for example. You would think that to maximize your fire rate for a non full auto scout, you would have to precisely press the trigger button at exactly 0.3000000 seconds to have it be comparable to full auto, right? Well, Destiny allows you to hit the trigger slightly earlier (like at the 0.25 second mark) and it will still fire the bullet at exactly 0.3 when full auto would have fired the next one. Those figures aren't exactly accurate, but you can definitely keep up with a full auto scout of the same archetype without using full auto since there's so much lenience with the timing.