I'm not running anything apart from hearthstone and HR. Using vmware on an SSD with 2 cores assigned (i7 4790k) but HS still ropes every now and then.
I've reduced maxwide to 4000 and it still ropes, and I've set silverfish.exe to high priority in task manager. I never rope when using the default HR AI.
CPU usage hovers at 80-90% with 2 cores, so its not like I'm starving it with resources.