On a perfect pitching staff, Giolito to me seems like an awesome #2 or perfect #3.
Aces are just so rare. But hey, it's true, aces do struggle too. Look at Sale this year. If nothing else, I think Giolito is still perfecting the repeatability of his delivery, and polishing the mental side of his game. If he doesn't lose any of his stuff, he will be perfectly fine.