I use EVGA Precision to auto-tune my fan speeds and when playing games such as Dead Space 3 and Skyrim on Ultra settings, my GPU generally only runs about 50C using 50-60% fan speed.

While playing ESO, my computer hits about 70-75C and around 60C with max fan speed.

Is it due to unoptimization?

I'm using the GTX 670.

I would argue it's the opposite and because of optimization. If it gets hotter, it means it use more of the hardware, no? If so, ESO takes advantage of the hardware more than Dead Space 3 and Skyrim.

Besides, the cooling should be able to take care of when the software use 100% of the hardware anyway, and graphic cards can handle 75C just fine.

This is not the place to talk about the beta.