Apparently people consider others opinions as being idiotic, if you want something else than 20man, without proper reasoning - at least in this thread. But I'm gonna be that "idiot" then. I saw a very nice post from a certain Legoshaman, and I would like to quote it here:

"The thing is this, i truly believe that the current format has crippled the PvE experience, we have seen guild disbands like never before, people are complaining on another level than before, allow me to elaborate:

1) when i say that guilds disband like never before its not because of the obvious reason that many might assume, namly that the content proves to difficult, i personally dont belive the mythic experience has been what blizzard wants us to belive its been, which is hard. Its not been easy, thats for sure, but it has not been that difficult either. What i do belive is that its so much harder to stableize a guild today compared to before, and this has to do with the high demand of people not having a defect in their gameplay. What 25 man raiding provided is that you could carry 2-3 people that was not up to par with the other raidcore, but that option is basically exctinct now, because if you do play poorly, you will wipe the raid almost every time. The high demand for excellent players is not a bad demand in theory, but in practice it has devestating effects.

2) People !@#$%. This is not new to WoW and it is not new to the human race, aslong as people are ahead of eachother, there will always be a heated conflict. This conflict is called "Please them all" which is an ideology i truly belive to be selfdestructive. Before WoD and the introduction to the Mythic format, people complained alot about various stuff within the raiding community such as, bosses being to class dependant or that classes were to weak/strong etc. The complaint that used to be common is now replaced with, guilds are dying or there is no room. We have people complaining about not even being able to raid on their servers because of the lack of space. People are forced to play on the maximum level of serious gaming, because lets face it, not many casual guilds will down these raids in time, before outgearing it and making dps checks moot. I know alot of you will probably object to this, but let be just flush it out really quick.

3) You should not have to realm swap to find a suitable guild, or you should not have to reroll to suit a guild, or you should not have to dedicate insane amounts of hours to achive the ultimate rewards for raiding, or you should not have to leave your friends or play different speccs because you main specc is meh.

These things should not exists in such a way that it becomes mandatory to do, if you want to compete on the maximum level( i do not mean the top 50, because there has to be another level above the ultimate one, but there is nothing in between anymore)

We need an eviroment for all people, blizzard killed the 10man experience, it was a perfect format for many people that did not want to raid with many strangers, or that felt they could achive greater things if the numbers of people did not hold them down.

I was dead certain that blizzard would acknowledge this in their presentation at gamescom, boy was i wrong, because it seems that the hundreds of threads regarding the raiding format has passed by like a soundless wind. I truly am dissapointed at the inability to adress such an important issue, that i belive is one of the major factors the subscription level is down to a rekordbreaking 5.6 million."

And I truly agree!