One super easy trick is to look at the Power Management setting on the server (Figure 1). If its set to 'Balanced', the server has known degradation issues. I first found this out here Microsoft Support - Degraded overall performance on Windows Server 2008 R2 back in late 2011.
By default, the 'Balanced' settings is used instead of 'High performance'. Why? Most computers will operate with highs and lows during the day instead of constantly being pegged at a high load. Windows Server dynamics performance scaling functionality is only active when in 'Balanced' so the power to performance ratio is optimized and is the 'greener' choice. As I understand, its a battle of efficiency vs being top of the game all the time and utilizing a lot of power unnecessarily. For a server like an AOS, I would almost always recommend 'High Performance.
About power manager feature:
MSDN - PPM in Windows 7 and Windows Server 2008 R2
Windows Server Blog - Power Management in Windows Server 2008 R2 – Improving your “gas mileage”