I have attempted in the past to get the RT-N66U working with TDS IPTV, when it had Merlin and stock firmwares. I could never get it to work correctly.
However, if you install DD-WRT on it, it gets many more options. This may work as I was able to configure a Netgear WNDR3700 with DD-WRT to work correctly with TDS. They have similar options. I never tried it with the Asus though, as it now is only my wireless AP, but I am running DD-WRT on it.
I have read that the stock Asus firmware and the Merlin firmware aren't quite up to par for Multicast routing/IGMP.
Another option you could do, if you have an older spare PC, is install PFSense on it, use it as your router and the Asus as a wireless AP as I am doing. PFSense is very easy to set up with TDS internet, and I have created a guide to configure the IPTV service to work with it.
Guide is here... »
TDS IPTV Service using PFSense - Configuration InstructionsGood luck with it.