We know that ESO will have 24 man content (i.e. raiding and I think its silly they don't call it as such, but whatever).
A few days ago, I was discussing it with another Raid leader friend of mine whether 24/25 man Raiding leads to a toxic community. We both came to the same conclusion that it does. I have been Raid Leader for multiple 25-man raids in WoW. Basically there are only 3 types of 25 man Raiding guilds. First is the rare and hyper organized guilds that can assemble 25 people with no problem. That's SUPER RARE and generally does not happen.
Then it is the type of guilds that I was usually part of. The ones that typically have 25 people who Raid consistently. Unfortunately, when its 24/ 25 people there will be always people who cant make it and then the nightmare begins. There were nights that I had to spam chat for 2 hours and not get a qualified people for Raiding. NOT A FUN PROCESS, which is why I think 25 man Raiding is bad. I have been in many top guilds in WoW and typically people would not be able to show up because of birthdates or other real life stuff. Then you have to spam chat for hours and many times cancel the Raid altogether. Its a terrible process.
There is only 1 type of guild that can do 25 man Raiding without huge problems and that's when it uses people as substitutes (i.e. not regular Raiders). Unfortunately, having people on the sidelines is not a good thing for the community. Its kinda of a [censored] thing to do (i.e. you are only going to Raid when we need you, otherwise get lost) and it does not create a good MMO community. Its a lot more cut-throat and ESO does NOT need that. I have experienced guilds with substitutes and its not a good thing. It will be really bad for the games community. ESO needs systems that lets people play together not be a cut-throat competition of who is going to Raid tonight and who is going to be left out. Not to mention the endless drama that it leads to. You just end up with a toxic community. Bad bad bad idea.
I feel very strongly that the ideal Raid size is 10 or 12. I am a little bit disappointed that ZOS says it wants to implement 24 man group content, when it has so many drawbacks. Ten or Twelve people is big enough to feel epic and you don't get the problems (toxic and cut-throat community or severe difficultly in finding replacements) that 24 man Raiding necessitates.
If ZOS does implement 24 people Raiding, I hope that they at least develop systems to accommodate that. For example an easy to use and detailed Board of people who want to Raid (and for which Raids) along with their stats and experience. Also maybe allow guilds to put a group of (lets say) 6 people together and then have a tool in-game that allows you to list your group for available Raids. This way its would be easier for a 24-man Raid Leader to recruit a lot of people at once for a Raid. Things of that nature. Otherwise, I am pretty confident that you will end up with a pretty toxic Raiding community. NOT a good thing. ---