I know that the legions are good in EB but they are not as good as they were historically, eg you cant win when massively outnumbered and even when you win against a equal sized force you casulties wont be too much less; but if you look at some of romes most impressive victories they had huge kill-death ratios.
Battle of Watling Street 250-1 outnumbered 23-1 is good example as is Alesia were all though casulties numbered 10,000 the romans were crushed between to forces both larger and still won killing 260,000 of the 330,000 warriors and captured 40,000 which is really a testement to the legions morale, resiliance
and sheer bloody toughness. Ps I know i only gave two examples but there are a huge number of battles (the majority where rome won were with very few casulties but inflicting many).