Plus the game is being updated. No game stays the same forever as far as performance requirements go. Eventually you have to bite the bullet and upgrade/buy a new pc. They don't do this to be jerks to the people running the game on old hardware, they do it to keep the game fresh and up with the times.
Just be happy you dont play a game like EvE online. That MMO has to be one of the most graphic intensive MMOs out there, and they are constantly updating it. It's beautiful but in order to run max settings on it you need to upgrade your hardware once every 2-3 years. You should be happy you got as many years out of your computer as you did.
:eave a post in the hardware section of the forums, maybe someone can steer you in the right direction as far as what you need to do to get better frame rates.