Well, good on you, did you remember that the three laws of robotics are from a book, which is all about how they do not work?
Just remember the case of telephone speech, every single one of your serfs has a unique understanding of those rules you gave them, those differences will cause them to go into conflict between themselves and other people.
Adding a "Do no subvert these laws" law will cause them to Inquisition each other whenever they believe that one them "subverted" a law.
Without a power that makes people understand you the way you want to be understood, people cannot really understand you and a power that does that would effectively be a type of brainwashing, where you add the information without their own natural biases, differences in memory and hearing and so on from modifying the words and intent.
Without a power that makes your serfs understand each other, ie. make them a hive mind essentially, they will perceive your rules being broken by others, due to lack of information and misunderstandings. IE. On of them thinks another saw a grimm and left it alive, without any reason, thus attacking and trying to subdue the rulebreaker, the rulebreaker defends themselves and tries to subdue his perceived rulebreaker, the second person, they will then proceed to either get a lucky incapacitate or kill each other.
A unique problem of sorts simply because unlike actual people, they cannot disobey and HAVE to punish and pursue rulebreakers.
