It's not the IP blocking that have made people quit this game.
This game doesn't really have anything left to offer. I've been playing for 5 years and it remains the same. A new raid comes out, new gear comes out, and I have to gear back up again. Oh wait, that's a pain in the ass because enchanting and enhancing is abysmal in this game. Good luck trying to be completely F2P and not spend a single $ gearing yourself with outstanding gear.
UI lag is getting worse and worse with each update. Even people with the best computers still have a hard time playing Vindi due to an old outdated engine that doesn't support multicore properly.
It drives people away. And with less people, means less people to try to find to do stuff with, resulting in other people leaving because why would they want to play a game that has 0 community? Vindictus had a good run for a little while and now it fell off, and with other games coming out and looking more promising, people are preparing and investing time to other games.