First of all thanks for appreciation.
You've figured it our correctly. Randomness suppose to prevent you from getting banned. Repetitive task executed with dead precision every time is easier to detect than something that is a bit random... at least some people believe that. But there is also other function to it. Some people - like my friend - play on shitty computers and in my friend's case nothing under 150ms will work.
About magic find. Level of Magic Find applied to the loot is taken from the moment you execute your final blow. As I observed it should be also applied if you for example die and monster will die off your bleeds etc. However I heard rumors that if some pets or followers are responsible for the final blow your MF is not applied.