I have had the same issue. it's not the GPU. it's the CPU's being throttled due to overheating. there's a membrane on the back panel that's there to filter out the dust in the air. after using the laptop for a few months it became blocked with all the dust and was practically impossible to clean. i just removed it today and already idle temp is 14-18 degrees lower. during playing a game even like Dota2, 10-15 minutes into it CPU reached 100 degrees. so naturally, the speed is throttled so that it doesn't burn out. i'll try the game later and see if i have any improvement