If you bought your oregano from Penzeys, it should be good. They are one of the better suppliers.
I have tried Greek oregano and Mexican oregano on pizzas, and prefer the Greek oregano which I grow in my back yard and use both fresh and dry for cooking and baking purposes. It's not always clear what oregano really is. I have read that what is often sold as oregano is not really oregano at all, but rather marjoram, which is apparently similar botanically. The Greek oregano is supposed to be better for Italian cooking, whereas the Mexican oregano is supposed to be better for Mexican cooking.
Do you process your Turkish oregano in any special way before using in your sauce? I saw a post on PMQ in which Pizza Shark recommends tht dried oregano be mixed in hot water in preparation for making the sauce. Specifically, he says that "Dried oregano takes time to release its flavor... More time than a 6 minute bake will allow. Take your oregano and mix it with hot water from the sauce recipe and heat it to a boil for a while. Then add that mix to your sauce." Foccaciaman also raised the issue of precooking the oregano, at Reply #64, at http://www.pizzamaking.com/forum/index.php?topic=361.msg3306#msg3306