I seem to have fixed my problem and here is how:
As a rule of thumb, one needs to set a firewall exception for online games in antivirus app and windows. So had I in the very beginning before even starting to play crpg. However, I discovered that my stupid Kaspersky simply recognized the launcher and game executable as brand new ones following the update. When I checked, I saw that the launcher was classified as 'low restricted' instead of 'trusted'. I had already marked both trusted but as I said, it seems like Kaspersky treats them as new executables after updates.
While firewall restrictions do not really explain FPS drops (although high pings could be attributed to that), I am pretty sure that fixing the aforementioned problem hugely recovered my FPS rate. I still have to stress test one particular map (don't know the name but it is the one with a backdoor that is accessed after climbing up some stairs) though. That one gave me monstrous lag right away, as soon as I spawned on the attacker side. Regardless, I am confident that I have largely solved the issue.
So, that is what works for me as of now. Let me know what you guys have to say about this.
