Goal scoring is goal scoring, if you can score you should be able to from anywhere in the attacking 3rd. THats why we like Alexis so much. Theo had his chances and did not take them.
I will always put the blame on Coquelin. You need ball players in that part of the midfield. Xhaka can liberate others, but he needs others around him to liberate too.
Cazorla works with Coquelin because they stand close together because they mask the others deficiencies (Cazorla not be able to run and Coquelin being terrible on the ball). Watch where Xhaka is on the pitch in relation to who he is partnering with in comparison to Coqzorla. Xhaka often ends up everywhere, but sometimes further back with the CBs. Coqzorla are often pushing up. Its different.
Elneny and Xhaka would be dynamic because Elneny doesnt have to be near Xhaka as Xhaka can find him, and Elneny moves it quickly. I think Xhaka and Ramsey would work well too because of Ramsey being a bit more forward.
The only person I really dont want partnering Xhaka is Santi because he that is a slow midfield which will expose us.