Yeah, but compare the two scenarios
Arsenal prior to signing Ozil, had an excellent second half of the season. They successfully bedded in Giroud, Cazorla was doing great, and Koscielny-Mertesacker were a promising partnership. They ended the season on a high. They cut several deadwood players from their squad. They started the season being blown out at home against Villa, but they recovered well by beating Spurs. Ramsey was imperious, Ozil was the icing on the cake. So they were on the rise prior to the Ozil signing.
We on the other hand after a legendary collapse that saw us relinquish the title to City, and subsequently bought Van Persie. Despite winning the league last season, all our attackers bar Van Persie had mediocre to poor seasons. Our midfield was non existent as usual. Our defense missed Vidic all of last season and his replacements were Rio a year younger, rawer versions of Jones and Smalling, and Evans. DDG was great. Our team play wasn't great. It was the same pass to Valencia, hope for the best. Difference was Van Persie. A year on, and he is injured. Without the underlying issues being addressed by Moyes or Ferguson.
I just don't see the similarities. Arsenal's signing of Ozil had the effect of raising the level of the entire team. Our signing of Van Persie just hid the fact we have had chronic underperformers in our ranks for a while.