If Alexander Savage were to be a 24 man raid, it would need to be as easy as Cloud of Darkness with the same loot lockout, rather than Coils.

Sometime's it's already difficult to get everyone in a static of 8 to show up on time (these 7 other players you form a friendly relationship with, which makes it easy to forgive them when they're incapable of showing up on time). Imagine 24, where there's a chance of 5 or more people not showing up on time or at all for one reason or another. You either HAVE TO skip raid night for those people, or risk locking them out of content by taking PuGs. The battle mechanics would also need to be watered down, as most Coil fights have that one mechanic that just needs one person to screw everything up. Imagine 23 people wiping because one person didn't follow a mechanic? It would be frustrating and progression would never be made.