Your system is behaving as it was designed to behave. As the amount of work your CPU does increases quite a few things happen. Firstly the full amount of voltage at the processors disposal is brought to bare. But Intel build in a fail-safe mechanism to protect the CPU this is simplistically what we term vDroop is. This vDroop causes the amount of available voltage to not be fully utilised in case there are fluctuations in the current that may go over the recommended limit and cause damage to your CPU.
Lots of folks feel they do not need this protection, I am not one of those, and they increase the LLC to even it out.
vDroop is not a bad thing. If your system is stable with the increase to the offset you have now applied let it me and simply enjoy the system.
To help us help you - please provide as much information about your system and the problem as possible.