Why does graves need 2k hp and 90 armor late game base line
He's a range character and while it's not unheard of for short range marksman to have a tad bit higher armor to compensate but for the most part they don't in order to give them a weakness to close range.
Graves has no such weakness his attacks get stronger as he gets in closer and since he builds like a bruiser and can easily get passed 3k hp with life steal to boot he's getting the best of both worlds of having marksman damage and bruiser tankiness. I'd be willing to overlook it if he like suffered at a distance greatly but since his smoke screen got changes/buffs it makes catching up to people and giving them the business end of his barrel extremely easy.
He's durable, mobile, has dps with his autos even through his reload mechanic, and burst through his spells. Truly a pain to deal with.