i have this problem. AoC allways started using a process rundll32, and sometimes i needed to launch the game two times to start it inmediately the game runs fast. but when the game runed and the process rundll32 was also running, i could finish that process that used 50% of cpu and my game kept runned all ok all fast.
but now the game doesnt starts that process rundll32 and now the game is giving lag very hard, now the game uses that 50% of cpu that was used by the process rundll32 before, but now the game is breaking up too many even only starting it in a standart match. i played it normally in 1920x1200 in huge wars and i didnt had any problem.
i have tryed installing new windows and updating drivers but nothing works. i only formated and put aoc without any install of anything and it worked perfectly before.

Hello let's go ahead and try to maximize your Game settings by doing the below,
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Also give this a try: https://www.youtube.com/watch?v=yhqmZO7YyD0

If you are still having problems after this please let us know and we will try other steps.