I think 8vs8 is bad idea for game.Even 12vs12 will be better

agree.

To have an additional four people, behind which you can hide and run between them?

to decrease the percentage of inqs present in battle
to make battle less 'boring' - more issues at a time, more things to look at
to decrease the big-now chance of NOT having some class in my team which is ususally the one that we lack
to make it nearly impossible to play 6vs8 just like it happens so often after the patch.

Are 4 reasons enough?

on 3k bvs maybe yes, but on +4k no.

+1 ice

Make 4k without money. By the time you maybe succeed, the game will be dead.
Yeah, that's another problem though.^^