You shouldnt really need to upgrade anything, I'm curious why your motherboard is running so hot though, might be worth reapplying thermal paste to the north and south bridge.
With these components you should easily be capable of running whatever graphics on RS3 and Overwatch. the i5 4460 is a well rated CPU and the GTX 960 is a bang for budget card. Not extremely powerfull but generally well optimized running on a good new architecture, its power consumption is also quite cost effective.
The drawback on your system is that you didnt make it yourself, any modifications will void its warranty. if you have any warranty left you might want to consider picking up the problem with the company that assembled it.
if you decide to replace the motherboard. go for something with a Z97 chipset. An SSD is a nice upgrade considering you currently arent using one but it wont improve games performance, itll speed up loading screens of games you have installed on it though. Textures will be loaded faster too from my experience with Fallout 4 on my SSD.
so, this is your best bet, contact the company that assembled it, if you cant, then strip your system, replace the thermal paste on the north and south bridge. Airflow shouldnt matter too much in a system case, this has already been debunked on
Linus Tech Tips.
(if your case was somehow really overheating you would also notice a considerable increase in temperatures on your other components. which leads me to believe this is a motherboard problem)
So, if it comes down to it, just get a new motherboard.