Your concern makes no sense. The players who left due to groups harrassing them were not affected by the banwave, nor should they. This is an objectively good thing that is happening that has shown zero downsides, but you’re imagining that it’ll target innocent folk or require too many resources from Blizzard.
Obviously Blizz recognizes leavers as a problem and have a means of detecting them. That’s a good thing. Are you advocating that they don’t do this?