I believe Blizzard rely 99% on Player Reports.
I believe Blizzard detect and ban Player software hacks.
I believe that Blizzard can easily detect (LCP or algorithms) 24/7 botters and do not care to investigate.*
*If they did, we'd see hundreds if not thousands of bots being wiped daily. Instead, this category of 24/7 botters, I believe, are mostly banned from Player Reports; Player Reports are free to Blizzard, and a pretty good indicator of recent activity. Who knows, maybe when a Player Report (botting) is submitted the accused's activity is immediately logged and later investigated by a GM or other staff and then actioned at some later date.
TLDR -beware the Player Reports, they are what get you banned.