Well I’m running a “worse” CPU than a 2500k!
It’s a Phenom II which is technically a dual core that I have unlocked using a motherboard feature to a quad and then clocked it up from its native 3.2GHz to 3.6GHz.
I too show 100% CPU load but my experience is smooth and I hardly ever see any stutters and I can count the number of times the game has crashed entirely, since I have owned the game, on one hand!
My GPU is a 680GTX with a 2GB frame buffer and my system RAM is only 8GB and this thing is STILL running all the new games that I have thrown at it!
I saw some slowdown in wolfenstein II but that’s the only recent game that has given my old rig any trouble, DOOM 2016 ran great on my system.
Naturally I’m not running games on ultra settings these days but its usually medium or high settings but I don’t expect this thing to be able to handle the new stuff on maxed out settings as its simply not capable of doing it