The Customer Support Forum is not Customer Support. It’s a Player to Player help desk with occasional help from a SFA Blue (Support Forum Agent).
That being said it’s pretty much impossible to prevent a DDOS attack, by its very nature using millions of bots, unless you have an obscene amount of bandwidth. Which is economically unfeasible for Blizzard compared to a company like Steam (300+ million users).
It seems the DDOS attacks were targeting the Race to World First (which is over now) and OnlyFang’s Hardcore raids (which they are disbanding it seems).