For any users still encountering this issue:
We apologize for the inconvenience and hope it helps to know that we believe we’ve found the issue – we should have a new version with the fix out as soon as we can.
In the interim, if you go to: brave://flags/#brave-adblock-cosmetic-filtering , enable this flag and relaunch, you should see CPU usage improve. Please let us know if this is not the case.
Thank you.