So sleeper sites are randomised to a certain threshold which adjusts randomly for spawns, the armour/hull hp adjusts for each spawn and each sleeper has unique resists.
There is no defined trigger but the sleepers prefer to use the method of the trigger, which exclusively uses either turrets or missiles so there has to be communication or observation to what is the trigger.
This should vary people’s ability to solo the sites or to run effective fleets in wormhole space and might reduce aggressive farming