Well its difficult to say cuz I bought this rig for sc only really, and just as I started getting in to it (in 1v1) I had to leave (in Feb) cuz I had business things to attend to, and when I came back (this is the first season I'm back) I started playing in teams and not 1v1 cuz I suck in 1v1 with hots due to not playing it till now.
So in 1v1 it never gave me an issue, and in 4v4 neither, but when it gets to 200/200 supply for all teams around the 22min - 25min mark and a battle goes down I start seeing some lag, but nothing major, and also only if there is some noob going 200/200 carriers and those little fuckers that go flying just mess with the lag a bit, or if in the middle of the battle a terran would scan for cloaked units, then that scan also causes some lag.
I have mentioned this to my friend that built the pc for me and he then said it can only be my ram, cuz I don't have like proper gaming ram, he said that my graphics card is more than capable of carrying the load and my i5 should not have any issues either. My sc is on my ssd drive so also should not have an issue. He suggested Corsair I cant really remember the name, or many details of it, but 8g was his recommended amount.