I get good fps (40-90) in editor, sometimes drops to 35 on medium-high settings.

In any multiplayer server, whether one I join or host, no matter the ping or server population, I get 15-30 fps, almost always around 17. Same exact video settings.

AMD FX-6200 @ 3.8 ghz (6 core)
GTX 660
8 GB G.Skill 1600 MHz
Arma 3 on 7200 RPM dedicated HDD.