As someone who has been attacking the Myanmar Government sites and their military servers since October, I can definitely tell you that DDOS attacks are very cheap considering the damage they can cause. Mind you the Burmese government has no idea of actual cybersecurity in comparison to blizzard, but the basis of DDOS and DOS has been constant for decades. Botnets can be purchased for very cheap especially in Russia/Asia. It has costs me about $200 since October to keep many Myanmar govt/e-commerce sites mostly downed.
Not advocating DDOS attacks fyi, I'm doing it as part of a resistance against an actual tyranny. My guess is this is just the typical angry gamer DDOS against blizzard, it happens every now and then.