Is there any need to ground every component to the case? Certainty I will ground the power supply with the attaching screws but do hard drives, motherboards and DVDs really need individual grounding or do attached cables accomplish this to a satisfactory degree?
More about :electrical grounding custom metal case
The PSU is not grounded from the screws, the power grid accomplishes that. If you install all the components normally, don't touch it.
If your motherboard has contact to metal, it would most likely short out and explode (assuming it's touching multiple metal contacts on the mobo). Just install a PC normally like everyone else and you'll be fine.
Most high quality cases have brass standoffs and the shiny solder around the mounting holes does make a ground contact for the motherboard this also helps in shielding the motherboard from interferance.
Also the power supply does have an earth ground that is why it has a 3 prong plug.