The #1 way botters are caught is because other people report them. Blizzard has a long history of being very slack in tracking down botters on their own. This is why you see so many botters in Diablo 2 and Diablo 3, as it very easy to sit in your own instanced solo game and bot forever. Eventually the games get overrun with bots. WoW has avoided this problem, mostly because have never offered elaborate instanced content that is designed for solo play.....until Torghast. These bots can overrun game systems and flood ladders or flood the economy with items. Blizzard does nothing. Absolutely nothing. The only way to stop that is to not offer any competitive system nor items in Torghast, which will ultimately make everyone lose interest in Torghast.
Randomly-generated maps are not a hindrance for botters, as botters have been circumventing that for 20 years in D2 and for years in D3.
It is certain that botters will flood WoW on Day 1 of the release of Torghast. The question is, will it fundamentally alter WoW and make it more of a game for botters? Or will Blizz strip Torghast of rewards to solve it and make Torghast feel useless?