Larger groups are already penalized by having more people to share the same amount of drops. But you can't just add more DDs because they step on each others' skillchains. You can't just add more nukers because of cumulative magic resistance. You can't just add more support because they become redundant and who wants to play a game where 12 out of 18 people in an alliance are support?

If nothing else, it has to be adjusted significantly.