I don't think that the 25 man people are understanding here. There are way way more 10 man heroic guilds (and players)
Wow Progress
10 Mans with at least 3 heroic kills: 18,957
25 Mans with At least 1 heroic kill: 4,692
So 25 mans all have to drop 5 people - That means there are 23,460 players looking for new guilds.
All ten mans would need to recruit 10 people - That means they need 379,140
So you don't need to do math to see the disparity of players. Essentially this means that blizzard is killing off ten man heroic guilds; they are not going to be able to adapt to this change.
If it was 15 man on the other hand the number work out better to even out the players in the existing scene... 15 is really the BEST option for maintaining guilds/friendships which is really why the "heroic" 10 man guild exists for.