The problem usually stems from combustion gases blowing by a weak seal at the injector tip. This creates the horrible black gunge that builds up around the injector and traps it in the recess.
I don't think any grease would stop this as it isn't due to electrolytic corrosion, but sealing the copper washer with the proper sealant is imperative.
This is all caused by the design of the common rail injetors. Due to requiring the high pressure fuel connections to connect to the rail the injector has to be able to sit at the correct position, as opposed to being screwed in until tight.
The fixing method is to clamp the injector body but through the ages this method of fixing has always resulted in blow-by after a while.
If anyone intends to keep a CR diesel it would probably pay to have the injectors and glow plugs removed and refitted at each service. I know this incurs cost but it is a lot cheaper than a stuck injector or plug.