I think you are correct about the lethal drug reaction during a rape, but to properly dispose of a body you need three things: a place, a plan and time. I do not think Deepak and Satish were around when she died. I think Joran was by himself at the Fisherman's Huts. My guess is he ran about 3 clicks to his house and told his dad what happened in full panic. After some conjecture, his dad helped him move the body back to the Sloot house. This move gives them the time to develop a plan and place for the body. Joran uses Steve Croes boat to dump the body the next evening within 2 miles west of Arashi beach... the currents and winds will move the body out to sea. When the Holloway family and friends showed late that night, the PvdS tried to create the Casino alibi not knowing how the plan ahd panned out. Joran returned to the house as Pvds lead the family on a tense goose chase.
This is sort of what I am thinking, except--here's where premeditation comes in for the father: Joran rapes Natalee and leaves her in a comatose state on the beach, either from suffocation or strangulation. Joran gets his father to come down, put her in VDS car, and take her to the house. How to clean upthe mess? Can't take her to Emergency Room without bringing down the whole VDS family.
Father advises to kill her and dispose of body. Method of murder? Complete the strangulation? Call Croese and inject an OD of heroin or other drug? Method of disposal: Croese,for a hefty fee, takes the body in a boat out to the Northern point and feeds it to the sharks.
I don't believe the Kalpoes were there if and when she died, but thought perhaps J called them up and demanded they help him get a boat, pressuring them with threats that they'd get arrested as accessories. Deepak knew the DJ, but that might be coincidence. Still rumor has it DJ has admitted someone wanted him to dump something at sea.
But Joran seems to have done as he pleased, staying out, gambling, drinking, maybe drugs, and his father didn't stop him, so Joran would have few fears about getting his father's help. This would make it plausible that he'd race home and involve his dad, whose livelihood and status on the island would plummet if this came out. Real fears for PVDS.