It seems like setting the test_cameraOverShoulder cvar while in combat does not have any effect. The camera just

This is noticable when you do Druid form changes during combat.

But it is particularly problematic for Worgens when you enter combat in Human form and get automatically transformed into Worgen in doing so. Because then we have no chance of setting the cvar value to fit the Worgen model...

(This Worgen issue has definitely not been like that before. It either got introduced with a new Patch or I have been able to set the cvar before the variable got locked when entering combat...)

Just checked and this is really only the case for the 8.1.5 PTR right now.
Hopefully this will not be carried over to retail when 8.1.5 goes live.

Not the case any more after another update of the PTR.