Game Discussions Monster Hunter World Owners
I just tried. I can confirm that it is a stuttering mess (as it's always been. One of the reasons I stopped playing), but I haven't observed any abnormal CPU usage (Ryzen 3600). Just two threads around 80% and the rest bouncing around a bit. Perhaps something specific to your model?
Some detective work later: Apparently Capcom in their grand wisdom decided to implement a new "anti-cheating anti-mods" system into their single player-co op game
Overheating CPUs and 100% usage is hitting a lot of players.
Runtime conclusion from people in the know is this:
"Capcom added anti-cheating / anti-tampering methods that is CPU intensive (the executable file is constantly being scanned by 24 anti-cheat thread checks running one at a time). These methods also causes windows defender and anti-viruses to scan the game files more often, likely resulting in the 100% CPU usage issue and high temperatures"
Amusingly the apparent "anti-cheating" methods implemented has already been cracked and defeated. Leaving you with a nice space heater in the shape of a computer to get you through the winter.
Yeah read about that too, apparently its only affecting customers who bought the expansion (which I didn't and will never be doing now) erasing hundreds out hours of play time.
I guess a typical MHW update, then. 
Though as a side note, I would like to point out that your temperature problem is not a fault of the game. Any decent cooler (within the specs for given CPU) should be able to cool down a CPU even when it's fully loaded.
Overheating means that you either overclocked it and the cooler can't handle it, or the thermal paste is old, or the cooler isn't properly mounted, or the CPU fan curve is messed up, or your case has bad airflow and/or is clogged with dust.
High temperatures then result in the CPU clocking down, which I'm sure only accentuates the game's issues.
Just to reiterate, because I got tangled in words, again (it's 3am) - temps are always a cooling problem, not a game's fault.
Though as a side note, I would like to point out that your temperature problem is not a fault of the game. Any decent cooler (within the specs for given CPU) should be able to cool down a CPU even when it's fully loaded.
Overheating means that you either overclocked it and the cooler can't handle it, or the thermal paste is old, or the cooler isn't properly mounted, or the CPU fan curve is messed up, or your case has bad airflow and/or is clogged with dust.
High temperatures then result in the CPU clocking down, which I'm sure only accentuates the game's issues.
Just to reiterate, because I got tangled in words, again (it's 3am) - temps are always a cooling problem, not a game's fault.