Capacity Planning Tool(s)/Log Parsing

i think you need two approaches to cover your whole requirements on capacity planning and monitoring.

at first, the static approach, a set of tools for capacity planning based on official or unofficial best practices on given OS and application platforms. for Windows OS and MS application servers, see below the MSDN article giving an overall considerations for an enterprise environment. the article is a bit of outdated on the products but the principles are the same for today.

Tools for Capacity Planning
https://msdn.microsoft.com/en-us/library/ms978394.aspx

the second is a dynamic approach, to monitor the related servers against given counters as you mentioned. be aware that this commonly is not based on event logs as there is no significant performance information available in the logs. instead, you need to run Windows Performance Monitor to provide a visual display of built-in performance counters, either in real time or as a way to review historical data (which is the data source for your baselines).

Overview of Windows Performance Monitor
https://technet.microsoft.com/en-us/library/cc749154.aspx 

just hope it helps,
bbao

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