I'll just say this though, any cards lower than an HD7750 or GTX650 I wouldn't recommend them at all for gaming. Okay, maybe the HD6670 is the cheapest card I recommend but that's it. Fortunately, flipkart has some 6670 around Rs. 5000. That's the best card you can get.
I believe BF3 is more demanding than GW2, and the latter is playable on mostly LOW settings at 1600x900 with a GDDR5 version of the HD6670. If you want Medium, I think you will be disappointed with anything less than a HD7750, also GDDR5.
Also, I did some research and you're really going to want to try to find a GDDR5 6670 if you can. There were differences beyond the type of VRAM used, and the GDDR5 version has a larger advantage than what you'd expect at first glance. You'll get probably 5-10 FPS more out of the GDDR5 version than the DDR3 one.