Australian military-wise, we operated the B, which was then modded to BA, without the compensator in the tail rotor hyd system.
Many, many practice hydraulics off approaches were flown without much in the way of dramas using the flight manual procedure of detecting the problem, slowing to an appropriate speed if required and then operating the hydraulic isolate switch to dump all pressure from the accumulators at once and proceeding to a running landing.
There was an accident where a student wasn't sufficiently strong to control the helicopter during a running landing and the instructor couldn't recover - they rolled it on its side on the grass. I don't know the full details of that one but I vaguely remember hearing it might have been that the hydraulic test switch was used to simulate the failure, but they didn't subsequently use the hydraulics isolate, which may have contributed to the problem.
Some time after I left, I believe they fitted the tail rotor compensator, probably after the investigation Shawn referred to? Perhaps someone in the know can elaborate on that.
Anyhow, my point is that in my experience, flying those variants of Squirrel / Astar with hydraulics off a lot (including hovering although that wasn't done as a rule), there wasn't a problem for the average pilot if flight manual procedures were followed. Maybe the other models are significantly harder, I don't know, but at least in the B and BA there was no big scary issue.