ram usage at 100% (16gb)

Hello,

I have a weird problem. Everytime i start my cataclysm client my ram usage goes up to 100% and it stays like this even though i close the application again. Only a restart of my computer solves this problem. My pc should easily handle this.

Ive downloaded the client again and i still have the same problem. I also play wotlk and i never had any issues there.
Do you guys have any suggestions for it?

here some specs:

Im using windows 10,
16gb ram(!)
i7 4790k
GTX 980

I forgot to add, my average ram usage in windows is like 3,5 - 4gb and every other game runs great!