HERE IS WHAT NEEDS TO BE DONE:
Scrap 10 man raiding. Scrap 25 man raiding. (25 man raiding is now running into the same problems 40 man raiding did.. thus getting scrapped.) 25 man raiding is a pain in the ass for raid leaders and with wow bleeding subs and 10 man being easier in the minds of most its just not what it used to be nor will it ever be again.
CHANGE ALL RAIDS TO A SINGLE 15 MAN LOCKOUT. Scale the fights appropriately. Add an extra item of loot to the table. 3 items drop. 4 on end bosses of each raid instance.
Its a win win situation.
Slightly increases raid leader responsibility of 10 man guilds.
Fixes the problem where 10 man guilds have 15-20 people who want to raid but the remainder get shafted and have to look elsewhere or have to make multiple 10 man teams that compete and cause guild drama because of what team players end up on.
Greatly reduced raiding responsibility for 25 man guilds. Have to recruit and find less people. Still get a decent amount of loot. Not quite as easy at 10 mans but not as unforgiving as 25.
25 man raids should only exist at this point as an LFR option to get as many people there as possible.
This would also open up the window for more time for blizzard to work on more content. Now they would only be tuning each instance to 3 difficulties (LFR and 15 man normal/heroic raids) as opposed to 5.