You may have to check out the WMI counters for another set that is used with ASP.NET v4. It's been a while since I did this and unfortunately the online documentation leaves a lot to be desired. I do recall that there was a version of ASP.NET that was newer than v2 that were still using those counters. I also suggest logging the data in a fashion that allows you to trend the values over time rather than just min, max & avg. You can do that with PerfMon which is included with Windows. Clearly the zeros you are getting for some of these counters mean that we aren't using the right ones b/c Requests Current, Request Wait Time & Request Execution time should not be zero on an active web site. The last time I did this analysis was with IIS 6.0 and maybe .NET 3.5. You may need different ones for .NET 4.0 and IIS 7.0. The basic concept is to find out if requests are getting stalled by a queue, particularly the Application Queue. When you find the right counters, you can tease out the total number of requests at polling time as well as any in the Application Queue. If there are any threads in the Application Queue, then there aren't enough threads to serve them at that time, and you can suspect some SQL queries aren't even being issued.
Since that may be more than you want to take on right now, I'd follow sqlrockstar's point and dig into the queries via Database Performance Analyzer and see if there are any to be concerned with. If not, then maybe a deep dive into the web server is worth it.
Good luck. I'll help you as best as I can from my recollection of how to do this.