System setup: Sabertooth 990FX, 8GB memory, Windows 7-64, AMD Phenom IIx4 970, GeForce GTX 560 - When playing GW2, and the screen starts to fill up with lots of other players, my CPU temp quickly climbs from the 50's C to 65-70C very quickly. CPu is clean and dust free - Is the GPU not picking up enough of the work, poor settings on my part for the video driver? or a bug, that seems to be the concensis of many other people having the same problem I'm currently using the latest GEforce driver 3-25-2013 and I've also tried using the EVGA driver as well. Thoughts? Do I need a better heatsink and fan? Not sure if the one I'm using came with the proc, or if I upgraded - its been a long, 22 hour work night and I'm quite tired. And no - no virus, bugs, or anything like that - Clean window install gives same results.
As more action occur on your screen, then CPU demands will increase and the CPU will be under heavier load, which results into more heat.
MMOs or other games with a large player-base often requires a strong CPU - Battlefield 3 multiplayer, Planetside 2, World of Warcraft are just a few examples of other CPU demanding games.
As you have the stock cooler then an aftermarket air or water cooler will help keeping your temperatures down. Also a fresh reinstall of your current heatsink with some quality thermal paste will also likely help on the temperatures.