Well I plucked that number out of my ass.
My point was that if they've done it right this time they can have an infinite number of instances, because only the ones actually in use will need to be loaded by the servers at any one time.
The huge 24+ hour maintenance at Patch 2.2 was to change the instance infrastructure to create and destroy instances as needed, and in a different post (that I cant find right now) they cited the future personal housing system as a reason to do so. So I'm pretty sure that's what they've done.
Quote:
This maintenance will introduce a new structure to the instance system that automatically adjusts the number of available instances according to the level of congestion. Until now, depending on the time of day, the number of players would become concentrated in certain content, maxing out the number of available instances, resulting in extended waiting times for players despite having a full party. With the implementation of this new system, more players than ever before will be able to participate simultaneously in the same content.
I also don't think it has anything (directly) to do with the massive lag on the 4-man instances at the moment. I have discovered that this infamous 4-man instance lag does not affect me, at all, even when the other 3 people are complaining about 20-30 seconds of nothing before fast-forward and jumping around nonsense. It sounds like another routing problem. Maybe the 4-man instance servers have been routed elsewhere.