i would've said its probably because rage is really badly coded like most bethesda games lol... but if its happening on other games to when it shouldn't be massively straining the card then i would look to do 2 things to start with.
1. get something to monitor and control fan speeds with on the gpu. the ati driver may not be running the fan at a sufficient speed. try getting msi afterburner. its based on riva tuner and will work with most graphics cards. its lets you set what speeds the fan goes at what temperatures. if you need help with the settings then just ask
i use this program and its great!
2. if this doesn't help much and you still think something is up i would try uninstalling and completely removing the graphics driver, reboot then reinstall the latest. there are some tools you can use to clean drivers out of your system but i haven't used anything like that for some time so not sure whats good right now. maybe someone else can make a suggestion on that....
good luck and do post back with your findings!