battle of the five armies errors?

[tom the eldest]

When dain's army arrive the is clearly four lines of dwarvish infantry.but when azog attack,only two respond to the threat.is this an error?and did the elves have been completely wipeout?because im not seeing anymore golden warrior after they tries to defend thranduil(and fail miserably,as per the fate of red shirt army).this even weirder because the elves seems to have a LOT of troops(clearly dain is outumbered by them,and the elven army is large enough to fill the space between erebor and dale),and that much troops couldnt have be killed in a few minutes.heck,the fewer dwarves survived.answer anyone?