So Graves can have a cigar

3 base AD off of an AA-reliant jungler isn't a nerf?

Okay. Let me put it simply: nerfing the AD, AS, or MS of any jungler is going to be several times more effective against them than against other champions. Consequentially, buffs to their AD, AS, or MS are way more effective than they'd be against other champions.

Nerfing their base AD or AS means their clears are slower (And potentially lethally slower, depending on how much it changes their damage against mini raptors), meaning they're less healthy, they get gold and exp slower, they can't gank as soon in the match...

And Graves's passive means that AD base is more effective on him. To achieve an equivalent nerf on, say, Ashe, you'd have to nerf her base AD by 10 or more.