There's a bug related to shadows that, on some systems, makes fps drop to single digits when inside any kind of a structure. It was admitted by Bioware - look it up in Dev Tracker, if you don't believe me.
There are also numerous problems with performance in Warzones - affecting many, many players (just look around the forums, you'll find countless threads about that, some of them hundreds of pages long).
Just because the game runs good on your setup, doesn't mean it's that way for others, peeps. Or that they, or their hardware, is at fault. We are, after all, talking about a fairly average looking game that should - according to official minimal and recommended requirements - run flawlessly on a several years old hardware.