https://bugs.winehq.org/show_bug.cgi?id=13470
--- Comment #29 from Federico Dossena info@fdossena.com --- (In reply to Stefan Lipsmeier from comment #28)
The 'Warhammer: Mark of Chaos Performance Fix' solved the slow loading bug for me. Just follow the instructions here: https://www.pcgamingwiki.com/wiki/Warhammer:_Mark_of_Chaos#Slow_loading. 2C_stuttering.2C_etc.
You will only have to replace one DLL in the games directory.
I am running game version 2.14 from GOG under Linux Mint. It fixed the issue running directly on Wine 5.0 and under Proton 7.0-5.
I made that fix a few months ago. In my article (https://fdossena.com/?p=whmoc/i.md) I explained the reason for the performance issue, it's not really a wine bug, the game has some leftover debug code that spams a system call that happens to be really slow on wine, so it's more of a combination of dev stupidity and a wine shortcoming.