Instancing is one issue. Combat logging is a different issue altogether. Without introducing a guaranteed method of determining whether a player combat logged or their connection has dropped for some other reason and also introducing an impartial third party (as other game clients in the instance cannot be trusted) method of handling the "lost" ship as an NPC (which would presumably try to evade attackers and leave the instance through hyper-jump or jump to SC then vanish), I don't see how the effects of Combat Logging can be lessened.
With all due respect, rolling over and giving up is not the solution. A lot of "combat logs" aren't even the traditional combat log, it's people in pythons, FDLs, condas, and other ships with strong shields. With the advent of shield boosters you can get all of these ships close to or well over 1000MJ of shields; it's no issue for people in large ships to pop a SCB, head to main menu, and exit after waiting 15 seconds. With 4 points to shields even with a full wing attacking them it's highly unlikely they will even lose shields, and even more unlikely that they actually will be killed before they finish the log out. This situation could be easily remedied by increasing the timer to 30 or 45 seconds.
On the subject of "ungraceful exits" as you people put as the definition for combat logging in the tradition sense, if I remember right telelmetry is already being logged on unexpected client crashes, and in this telemetry different aspects are logged, such as "number of human players nearby" and "under fire" and "in immediate danger". I'd say this gives a partially adequate method of feedback of determining whether someone combat logged, and at the very least it's a start. A decent solution would be a system like many other games that punishes an unexpected absence (dota or csgo for example); on the first offence do nothing; second offense do a 2 hr ban, 3rd offense 8hrs, 4th offense 1 day, then 3, 7, 14, etc days; with the punishment stepping up for each log. Accidental logouts, crashes and loss of connections could be identified using the aforementioned telemetry, and in the event that someone honest-to-god did lose connection during a pvp engagement, they would most likely not have a prior history of combat logging and only get a warning or 30min-2hr ban.
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You are not referring to Combat Logging as defined by Frontier (Sandro) in the OP of
this thread. What you are talking about here is graceful exit from the game when the ship is in danger (which incurs the 15 second delay timer). If Frontier didn't want to allow players to do this, it would not be an option on the exit menu when the ship is in danger.
I only just saw your response to this, and to address this again, if it is intended this is a very, very bad game mechanic, as it allows players in larger ships to stock up on a shield tanking loadout and immediately log out whenever they are in danger. Essentially it gives people who spend 50mil+credits on a ship a get out of jail free card, which is so completely broken and unbalanced I'm not even going to get into all the problems with it.