You shouldn't be concerned by that memory usage. Starcraft will just take as much memory as it is possible. Most of the time this memory isn't used - just reserved. You can check all of it in your Resource Monitor (it's accesible from Task Manager). You will see there whick amount of memory is being used, which is reserved and how much of your RAM is ready to be given to other applications.

So even if your memory usage looks high you can usually still run some additional applications, cause they will take unused memory from sc2 and everything should work allright. CPU meter can go wild but whole thing should work fluently