There are great benefits to closely monitoring your Active Directory domain controllers. Here are some lists of daily, weekly, and monthly tasks.
Network Steve Forum:
Looking at the suggestion in the Network Steve post one suggestion is using several CLI tools to create a report.
Expect to see some errors using DCDIAG in certain situations: DCDIAG.EXE /E or /A or /C expected errors (MS Support)
You will notice that REPLMON is no longer available in Windows Server 2008 R2.
Ask the Directory Services Team Blog:
NETDIAG is also no longer supported, but DCDIAG should give you all the information and ability that you need.