The default MSFS nav data is incorrect. I just checked the default BGL containing EHK using Hervé Sors’ “EasyNavs” utility program, and it shows the variation is set to 11.1 degrees East, which certainly explains why the OP’s flight path was 5 degrees off.
The Navigraph parameters for EHK in their beta nav data for MSFS has the correct 1965 value of 16 degrees East.
VOR radials on published charts are never, under any circumstances, corrected to current magnetic variation. A VOR radial is not a magnetic heading - it is the number of electrical degrees that the radial is rotated from the zero degree reference radial of the VOR. The zero degree radial points to where the magnetic North Pole was located on the date the VOR was put in service, which is not necessarily where the pole is located today.
In its internal operation, a VOR receiver measures the electrical phase difference between the VOR zero degree radial, and the radial where the aircraft is currently positioned.
The number on the VOR rose on a chart associated with a specific airway is not the compass heading to fly - it is the OBS course setting to use.
To fly a specific radial, the pilot’s only task is to set the OBS to the published course, and to fly the radial (inbound or outbound) keeping the CDI needle centered. As long as those two tasks are accomplished, the aircraft’s path over the ground will follow the radial path, whether the VOR was calibrated 2 weeks ago, or two decades ago.
In the rare case that a VOR zero degree radial was calibrated recently, then (and only then) will the magnetic heading and OBS course correspond when tracking the radial. It is much more likely that the VOR calibration is quite dated, in which case the OBS course and the magnetic heading required to fly it will differ by the difference between magnetic variation today, and the variation that existed when the VOR was last calibrated.
This assumes a zero-wind situation. As a practical matter, with any amount of crosswind, there will be a wind correction angle applied that would cause the OBS course and aircraft magnetic heading to differ, even if the VOR has a recent calibration to magnetic north.