What's your SQL Build no ? Also try to collect these counters (Perfmon) which gives us more insight ..

Processor – %Privileged Time

Processor – %Processor Time

Processor – %Interrupt Time

Processor – Interrupts\Sec

Process(sqlservr) - %Processor Time

System – Processor Queue Length

System - Processor Queue Length

System - Context Switches/sec

SQLServer:SQL Statistics Compilations/sec

SQLServer:SQL Statistics Re-Compilations/sec

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SQLBuddy