I'm gonna throw in my 2 pennoth here.
What the VCU does is to lock front and rear wheel rates together. But allow for a bit of slip so you dont smash the transmission when doing tight corners.
Its a remarkably simple and effective way to get permanent 4WD on a vehicle without having complicated gubbins in the car to engage it etc.
So what the VCU has to do is be stiff enough to transfer some power to the rear wheels when the front are spinning, but not so stiff that the transmission winds up when turning a tight corner.
I am going to make the radical suggestion that the stiffness levels of those two conditions are MILES apart, and provided the VCU is somewhere in that range its 'working well enough'.
That is, unless its totally and utterly siezed solid, there is probably enough slip to avoid damaging the transmission, and unless its totally spinning freely by hand, there is enough stiffness to provide the get-out-of-mud-free card.
Judging by talking to people who fix hippos, its very rare to get the VCU gone, but its a great money spinner for garages.
I am suggesting that people not wrry about their VCUs - by all means do the torque test, but remember, the only thing a really stiff VCU will do is take a long time to unwind any front-rear wheel speed differential, and as long as it has some give and you dont spend your time going round and round in small circles, you wont be damaging transmission, In fact those of us who had locked solid 4WD in the old days on landies will know the sound of a rabbit hopping landy that unwound its transmission when a wheel skipped over a bump.
So its unlikely that anything bar a totally locked solid VCU will damage anything. Except the two items that go anyway - the centre rubber mounted VCU bearings.
I'd suggest that peole change those with good quality units and run their hippos 1000 miles or so if they get what they think are 'vcu issues' ...chances are that will solve any issues.