Hi Camattin,
Open the Web User Interface (WebUI) of the DIR-655 in you web browser, you'll want to navigate to the STATUS tab and INTERNET SESSIONS page. This is a listing of all currently open communications to the Internet (anything with *.*.*.*:* is a Virtual Server, Port forward, Special Application, or UPnP Dynamic Entry). You'll need to locate any entry with your TA (reserved IP) then look at the corresponding Priority column. It's should have the QoS Priority that you had assigned it. If not, we need to make not of the ports being utilized by the majority of the communication; that's the ":#####" (where is # a numeric value from 1-65535).
So, once we have that list of ports, you'll want to transpose them to the actual entry you made in the QoS rules (just edit the rule appropriately). Let us know, if the INTERNET SESSIONS table is still showing the wrong priority being assigned. Also, as always, make sure you have the latest firmware version loaded for the DIR-655.