I believe that this being a 24 player instance is designed to assist getting people into content that are not necessarily invited to coils on their server for one reason or another, at the same time as allowing players that do their encounters via duty finder to participate in this content without worrying that one person dying will hold them back. The ability to down an 8 player boss is almost crippled at the loss of a dps, however in a 24 player encounter, perhaps the balance is not so tipped?

I suppose a question from me would be, is it going to be refillable if someone leaves, or will 20 people have to leave and re-queue at the loss of 4?
Also, are there plans to allow role change inside this instance, should a group find a lack in one particular role?