I've also been thinking about this a bit and had the following thoughts.
1. I have a hard time imagining that 100 PSI would be enough to move the sliding member and keep the OD engaged, when it is designed for ~360 PSI. If it is engaging at this pressure, it is just barely doing so.
2. When you engage the OD, the pressure should drop momentarily and then quickly rise to the original 360 PSI value, not remain low.
So, clearly, something is wrong with the pressure or the measurement. Since the OD appears to be engaging and disengaging as it should, I suspect the measurement. I think this has to be resolved before we can say much more.
One important point: the condition of the balls in the antireturn valve and actuator valve are critical. Even small scratches can cause a drop in pressure, although it's hard for me to imagine a 200 PSI decrease unless the scratch is pretty obvious.
You also might want to check the way that the pressure gauge is connected to the OD. It would not be hard to do that in a way that interfered with the ball in the actuating valve, and lose fluid through the return orifice.
As for the original question, re hard engagement: you are suddenly switching in a gear with a 0.8 ratio. I have a hard time seeing how that would not cause hard engagement. In mine, the shock is tolerable in 4th gear, but not in lower gears, so I always clutch it. Also, I would think that low pressure, if anything, would cause softer, not harder, engagement.