The answer is no. They have not changed anything that effects AFK. Well, not in the sense that you are referring to. It is caused by high server loads for the most part. That and visiting other sites while logged in to the game.
I have the same issue. However, it only effects certain areas. Example, in Deepholm I was disconnected many times during the Stonehearth quest line. I was guarantee to be disconnected if I switch to surfing WoW Head, WoW forums, etc, etc, while logged in to World of Warcraft in the Stonehearth area and the area just to the north of it. That was because of the amount of data that was sent from the server. The server normally sends less than 2KB with few-second-spikes up to 30KB. This wasn't the case in this particular area. I continually had a 15 to 25KB streaming from the server while in this area of Deepholm. Again, it only happens in certain areas. I can be in Org during prime time with slight lag in comparison of my normal lag.
Other effected areas were two spots in Hyjal. One was the area that everyone is first ported to. The second effected area around the Circle of Cinders.
I found few short-term solutions on the official WoW forums from a Blizzard Blue. One is disable add-ons since of them uses bandwidth to talk to other players. An example would the GearScore add-on. Also, discontinuing surfing sites and limit what other system application that uses bandwidth while logged in to WoW. Here is another, which happen to surprise me, disable the your Combat Chat via removing the filters. Here is a link to the post I refer to.