I'm using Firefox (159.0, so latest version).
How the souls are rendered is maybe something to also look at. Lots of bodies, lead to a lot of souls and when combined with March of the dead, it would quite tank the fps, especially near the end.
And when we had messages (the one where you had to click "Next" to dismiss them), I felt like like I had to click them twice instead of once.
Once the update is up I will give another go.