Welcome to PC gaming. This happens a lot. We get shytty, unoptimized ports all the time. You gotta get used to it. It's the norm with a lot of these developers (Ubi being the worst)
GTA and MGSV are not the norm. Most AAA PC games have optimization problems in the beginning. Some get fixed, some don't (*cough* Akham Knight *cough*)
PC gaming ain't all rosey (in fact, it can really, really, really piss you off).
But when it works, it's
But on the real, you gotta get used to bad ports. It's part of being a pc gamer. Don't even get me started with sli or triple monitor support either...