Using the Netflix app on an iOS device through a DDWRT will have issues with dsnmasq enabled. You can either disable that or manually set an ip address and dns server (for example I used google's dns on your iOS device to 188.8.131.52) on your iOS device.
Once you make this change you should now be able to stream Netflix to your iOS device.
I do not work for Buffalo Technology. My advice is my own and comes from my experience working with the products.