Hydraulics off, the controls can overcome even the tightest friction in some cases. Some aircraft are totally uncontrollable without hydraulics, and thus are required to have two independent systems. Some have only one system, but are only marginally controllable without it. The only time I would turn the hydraulics off in any helicopter would be for required checks or training. I've done hydraulics off landings in the AS350, but it's a handful, and you have to stay on top of it. Give it a minute or two without any intervention, and bad things may happen. With the hydraulics working and the friction tight, nothing should move. But I still wouldn't risk exiting with the engine running unless it was really, really necessary.