Blizzard’s policy is that they don’t give a crap about anything unless someone/something is flagged enough to trigger whatever threshold they set on it. It’s a majority vote system, and is as terrible as it sounds. A majority of pricks/trolls easily outvote a minority of good people, meaning you get hit while they are not.
Best solution is to not engage with them at all. My block list on the forum is a mile long. You can flag/report, but as I said before, it won’t do anything unless enough other people do it too.
Here’s an example of one that still trolls my posts regularly, even though I blocked ages ago and haven’t seen or responded to any of it since. They usually give up and move on at some point when they don’t get any attention though. Blizzard and whatever channels they troll don’t give them any, and that’s the right call. “Don’t feed the trolls.”