Most people at the Ex-raid I went to last week were more concerned with catching MewTwo rather than items. Therefore groups were sized (20ish) for certainty rather than optimization. Despite most people only having 6-9 balls, over half caught Mewtwo.
While I understand that an optimized group size/makeup can yield more balls for everybody, there are usually more casuals that don't understand this strategy than everyday players that do. These people are more afraid of not defeating the boss than they are about having 1-2 more balls. The scene is pretty chaotic with 60+ people hanging around a small area. So trying to have a reasoned debate with 10+ people who don't understand the strategy at the same time is nigh on impossible.
I'm trying to figure what size group to use. Instinct has 14 level 34+, while my Mystic/Valor group only has 11 (unless randoms show up). While that seems like enough people, most are below level 34 and I know the teams of about half of them (most have only 1 ttar and it's level 20)