Paulinho has been **** poor so far. I've tried to be patient with him, but he's a midfielder who is not good at anything at all. Okay, maybe one thing. He makes runs into penalty area, but when that is your only good quality as a midfielder, you have to score goals. So far he's got one in the league. The fact that the team is not creating a lot of chances doesn't help, but he has also missed a few good opportunities.
Apart from that, he can't pass the ball, he is technically limited, he is not very good defensively positionally, he doesn't win possession, he really does nothing. Jenas got a lot of stick on this forum, deservedly to a degree, but he was usually better than Paulinho has been for us so far.
I was worried after seeing him in the Confederation Cup too. I could see that he was a very limited player. Along with Hulk he stood out as Brazil's worst player in that team.
Dembele certianly has his faults too. He lacks vision and passing ability/passing creativity. But at least he can go past his man and create openings that way. He also retains possession better, is physically stronger, and does a better job defensively. I wish Dembele would play with more ambition. For example, on one occassion against City, he advanced with the ball through the middle, went past a couple of players, and managed to release the ball to create a chance for Adebayor. He should do those things more often, as he has the ability to do so.