Clarification of the Fundamental Issue
You don't grasp the fundamental issue at hand. Does Annie drop her crazy ability burst damage on you and then proceed to deal autoattack damage comparable to Tristana, Ashe, or Miss Fortune? Does LeBlanc press Q + R to burst your health down and then activate an attack speed boost and destroy you with Infinity Edge and Phantom Dancer? No, because they are burst mages, not AD Ranged Carries. Graves is both.
From levels 7 through 14 his Abilities start to see a huge decline. His Q does not scale with AD, obviously, and his R does not either. During this time he is sort of 'meh' in the sense that yeah, he can still use Q and R to do damage, but he must, MUST supplement the damage with Quickdraw. He dashes in, uses Q and R for his 'damage' and then has to either hope that A.) His team CC's the person he is attacking, or B.) The enemy does not look at him. If they do? BOOM Dead.
Now 14 through 18? Hooo boy. If the game has gone on this long Graves is no longer viable in the way he needs or is shown to play. He has to operate more like an Assassin. He does not carry, he does not do damage with his auto attacks OR his abilities unless the game gods have been kind and someone on bottom thought "Hey, Graves is weak up close! I'm going to try and get in his face EVERY SINGLE TIME."
He relies on his steroid to attack as fast as humanly possible. Only problem is, unlike other champs who build huge amounts of attack speed and are AD carries, Graves does not have a reliable way of getting out of battle.
What? You say he has his dash? Sure at level 18 with a full item build you can probably attack fast enough to get his dash on a 5 second cooldown as long as you are shooting, but that's still dashing in, potentially getting nuked just as fast as any squishy AD in melee, and still have to get out without being CC'd hopefully.