Strange performance issues

[ButtSlark]

Description

Recently re-installed Dota 2 and I've been having some ridiculous performance dips which I don't experience in any other game or application:

Back in November, I had no issues with performance on this very same computer. The game ran at 144FPS perfectly fine at all times. Now, the game only runs fine at 144FPS (my maximum limit) in the menu. Once I load into the game, however, it drops.

• The FPS counter RAPIDLY flicks between 100-140 FPS, tens of times a second, to the point that the numbers are a total blur
• My CPU (Ryzen 5800HS) usage and temperatures are extremely low (60-70 degrees). Dota 2 uses at most 10% of a SINGLE core, and nothing more.
• My GPU (RTX 3080 laptop) usage and temperatures ALSO stay extremely low (50~ degrees=). GPU usage never goes above 40%

Despite this, the game will slowly drop in FPS as a match progresses, dropping to the 70s before long, and below 25 in teamfights. As this occurs, processor and GPU usage continue to drop, rather than increase.

If I change any of the graphics settings (normally set to maxed out) to anything lower, the FPS and patterns stay the same, but system resource usage just goes down. Even when I drop everything to absolute minimum settings, including ridiculous (40%) image scaling, my performance stays exactly identical.

Again, I have experienced no such issues with any other game. So far to fix it, I have tried:

• Changing API to vulkan, DX9, OpenGL, and back to DX11
• Reinstalling the game, both normally and from two other steam servers (in case of corrupt files on one)
• Purging all graphics drivers from my PC and installing fresh ones
• Changing every setting in the NVIDIA control panel
• Changing processor priority to high
• Changing power plan
• Running the game with no other applications open in the background
• Disabling steam overlay
• A bunch of different launch options to enable or disable FPS limits, VSYNC, etc.

Thank you for getting through my large post. I've been doing my best to find a fix myself but I cannot find anyone else with a similar issue online. Any insights would be much appreciated. Have a lovely day!

Example Match ID (and possibly Timestamp)

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Screenshots

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[itsmehdi97]

I've had the exact same issue after reinstalling the game yesterday. Before that the game would have run normally with 70-90 FPS, but after reinstalling it barely reaches to 30.