You are way too harsh on Marchisio, man. He's an excellent midfielder. Wonderful workrate, great at positioning and movement, very good passer of the ball and he will score you some goals over the course over a season. I've also always been very impressed with his link-up play. I'd start him over Nainggolan any time.
That isn't to say he's better than Pogba. Paul Pogba is put simply a phenomenon, a very very rare talent. But it's great to have both of them in the squad
And I agree with a post @JuveJay made yesterday. This is a potential 50+ game season. Both of them will see plenty of gametime.