Im switching back to brackets because webstorm is completely broken for me in a similar setup to the one you described (react/filewatcher).
My issue is actually worse though, because periodically webstorm deletes files and creates versions of them with .jsjb_old. and leaves a file lock, so I have to reboot to actually rename/fix the files.
I can also confirm that I experience the same performance issues you described running a new i7, with 12GB of RAM. Unfortunately its the worst IDE I've ever used.
Fortunately I'm still on a trial version. I would be pretty upset if I just paid for an IDE that deletes files and freezes like this.