I agree with you, the iogear usb bluetooth is not recognized as official apple, so it most likely locks all the features out. A usb made with an official apple card sounds like it is should allow you (with the all ready installed ac card) to complete the needed hardware.
Let me ask a couple more questions.
1. Did you use the iMac 2013 wifi card? Did you need a converter listed in the first post, or does the 2011 iMac have the needed slot for the 2013 ac wifi card without the adapter? sorry, it is hard for me to tell from the online pictures if the connector is the same or not.
2. Looking a a tear down from ifixit, there are 3 cables for wifi (one all black, 1 black with 1 white stripe, and 1 black with 2 white stripes.). The ac/bluetooth card has 4 terminals. Which terminal did you attach each wire to? Which one was left bare?
3. Do you think that unplugging the existing bluetooth board would be advisable, so it doesn't conflict with an official apple homemade usb bluetooth?
Thanks, very hesitant to open up my iMac, but it might be the best option and this kind of info is good to know.