This is a known problem as far as I've read from the forums.
A workaround to fix it on multicore cpus atm is to change the core affinity of the process to use cores 2 (,3 and 4.) By doing a .bat file which starts the game with using only cores 2-4 you don't have to go set the core affinity manually every time you start the game. This actually won't cause the game to use all the allocated cores but at least it moves the load off the 1st core, helping a bit with the heating issue and making the game run better.
Just make a new document with notepad, enter the corresponding line (depending wether you have a quad or dual core) in the file and correct the path to your game folder. Save as wot.bat (remember to switch the pull down -menu option into all files instead of .txt text file when saving) and start the game using it.
Quad core: c:\windows\system32\cmd.exe /C start /affinity E D:\Games\World_of_Tanks_closed_Beta\WorldOfTanks.exe
Dual core: c:\windows\system32\cmd.exe /C start /affinity 2 D:\Games\World_of_Tanks_closed_Beta\WorldOfTanks.exe
Step-by-step:
1. Open notepad
2a. If your computer has a quad core processor, copy this and paste it in the notepad c:\windows\system32\cmd.exe /C start /affinity E D:\Games\World_of_Tanks_closed_Beta\WorldOfTanks.exe
2b. If your computer has a dual core processor, copy this and paste it in the notepad c:\windows\system32\cmd.exe /C start /affinity 2 D:\Games\World_of_Tanks_closed_Beta\WorldOfTanks.exe
3. Change the part "D:\Games\World_of_Tanks_closed_Beta\" to the corresponding location on your computer, don't touch the WorldOfTanks.exe though.
4. From the top right corner of the Notepad-program, left click "File", then left click "Save as..."
5. Write "WoT.bat" in the save as name field. Don't click save yet.
6. Under the typing field, there's a pull-down menu. Left click it and choose "All Files" instead of the "Text Documents (*.txt)"
7. Now left click save
8. Start World of Tanks by double clicking the WoT.bat file you just made.
9. Enjoy!