energy dissipation (=power=heat generation rate) is proportional to the square of fluid velocity (which is related to the velocity of the piston in a generic linear viscous damper), but I don’t think that necessarily relates directly to damper "openness".
force generated by the damper is a function of the fluid velocity and the size of the restriction oil has to flow through. But that force acts to slow the velocity (whole point of having a damper), so velocity is constantly changing rather than constant as in the simple example above. If you change the size of the restriction (opening/closing damping circuit), it changes the flow characteristics which affects the force generated and therefore how the damper slows the velocity and therefore how much heat is generated during the stroke.
If we simplify by assuming the damper experiences the same velocity and just vary the orifice area, a “more open” damper will actually dissipate less energy because the force generated is lower than the “more closed” case. (But this is a little unrealistic, since if the damper is doing it’s job it should be slowing the velocity)
My gut tells me that the graph would actually look more like a mirrored image of what OP shows as Option 3, ie high energy dissipation when highly damped, less when less damped. Which makes intuitive sense based on what a damper is supposed to do. Although I would argue that the end cases are never 0: if fully shut (no flow) the shock is going to be hydraulically locked unless there is a bypass (well, ok, I guess 0 velocity makes it 0, but not a useful 0). If fully open, you still have some viscous fluid flow which will dissipate energy.
But I don’t think it’s necessarily linear - probably could be mostly linear in some portion of the curve with correct design choices. But keep in mind a real damper may also have some combo of separately tuneable high speed/low speed/compression/rebound circuits. Have at it.
Regardless, it isn’t something that is robbing any useful energy from your ride.
Disclaimer: I know enough to be dangerous but without breaking out some old fluids textbooks may not know enough to be right! And I’m not that bored 🤓