First the clarification, the timer system that works behind the scenes is meant to be exactly that, behind the scenes. No you can't afk the system, there are a lot of moving pieces to it and we talked about it extensively before we implemented it to guarantee its not exploitable. At it's heart Diablo is a game about slaughtering demons and getting random cool rewards. The system that is in place should never be experienced by 99% of the population, it's there for the 1% who just get really bad random rolls for an excessively long period of time. If we want you to get a legendary every 2 hours, the system basically says "ok it's been like double/triple that period of time, just help the guy out!"