Here are Ozil's stats from his last season at Madrid and 1st season at Arsenal courtesy of mixedknuts on twitter. The graphics are scaled so that a player in the top 5% is outside the largest circle and bottom 5% is inside the smallest circle. As you can see they are quite alike. He could do better with his scoring and goal conversion %. Its not too surprising that his throughballs dropped going from the Madrid attack to Giroud, Cazorla, Podolski, and Walcott being injured for a lot of the season.
Ozil is basically the same player he was at Madrid. His statistics would almost surely improve if he was playing through balls for Aguero instead of Giroud. For a player in his prime that Arsenal bought for £42.5M, City buying him for £32M a year later would be great business.