Mine is a Gigabyte not XFX but I would assume it shouldn't be too far apart in terms of temperature of the card. Mine idle at 30, in game around 40 no more then 50. I do have the card fan control set to auto so i didn't really pay too much attention to the fan speed. It does has a lot to do with the ambient temperature and your case ventilation though, I do have 1x140, 2x80 and 1x120 fan forcing air in and 2x120 fan pulling out at the top all, although i have H80i setup forcing air in (meaning stupidly forcing hot air inward) and ALL fans were set to the slowest speed but my R280 still not even close to your temperature. With all that being said 40C isn't crazy at all, in fact is well within normal operation range.