I like to tweak the settings so that i get a constant 60 FPS. When doing this, however, I noticed that lowering the settings gives very marginal gains to framerate and in some cases *worse* framerate. An example of worse framerate is that I'd get 60 FPS in a typical scene of my base and some units. This is on Ultra settings with all graphics options at the highest possible value. When I choose the following:
Post-Processing: Medium (automatically changed when Shaders is switched from Ultra to High)
My framerate will drop from 60 FPS to 24 FPS on average. This is the one instance where my performance *drops* when I *lower* the graphical settings.
Another peculiar example is during one of my replays which contains high-action moments. I'd fast-forward the replay until I get into a 4v4 battle with tons of units, bases, and special FX. The framerate during this scene at 1920x1200 is about 47 FPS average. This is OK. So, in order to get the framerate bumped-up to a 60 FPS average (so there are no erratic swings in rough framerate), I lowered the resolution to 1680x1050. To my surprise, the framerate was the same! So I chose an even lower 16:10 resolution which was 1280x800, and the framerate was STILL the same!!
Confused as to how the performance seems to never improve proportionally with changes in graphical settings, I just set the overall Graphics Quality to Low. Now, there was an improvement, but only about 10-20 FPS in the least intense/empty areas of the map!
What's the deal? I can't seem to win with graphical settings. An obvious reply would be "your computer is obviously bottlenecking elsewhere like your CPU". I would respond with my experiences with one of the many other games I own. I've always been able to change the settings to witness improving performance. This is within games like Crysis, Metro 2033, Dirt 2 (even in 3-montior Eyefinity modes), and Bad Company 2. Every single one of these games yields a constant 60 FPS at 1920x1200 (so obviously the framerate is higher than 60 FPS if vsync is turned off, and I've "cleared" my monitor's refresh rate threshold).