Gas discharge devices would only be needed in lighting prone areas, and if the dish is the highest metal object at that location, if mounted on or close to a building with a higher structure then the dish, it would be safe to just ground the dish by bonding it to ground and use a ground block for the coax.
Now if the system has an external Diseqc LNB switch with a metal body you can use it to ground the system.
If the dish is out on it's own on a metal pole and is a big dish I would use a gas discharge device if you get lightning storms in your area, better safe then sorry.
If planning a new big dish system ("C" band) I use about 5 meters of #6 bare copper wire and make up a spiral as big as the bottom of the hole for the base of the pole the dish is going to be mounting to, then run enough of this ground wire up the pole to ground the dish and the system to it, once the hole for the base is filled with concrete it will serve as a good Earth ground for the system.
In areas with very high chances for a direct hit (Florida come to mind) I use lighting rods to protect the RF system, there are static bleeders available for big systems bur are expensive.
For more info on this, this company comes to mind,
Lightning Rods, Air Terminals, Conductors, Cables, Grounding Systems & Lightning Protection Systems | Thompson Lightning Protection
