That is my problem with elves in war - they either must be one- elf - army/or ,at least,company/ or they would be wiped out in less then 1000 years,even if they win every battle.
That is also problem with all settling except LOTR./there are logical reasons why elves there do not need fight much or enemy who could kill many of them/
But Warhammer Fantasy ? in real world,all elves faction would vanish after less then 500 years,all dwarves after less then 1000,and after 2000 years we should have only goblins,skaven,undead and maybe Slann.
Becouse all human except undead one would be replaced,too.
So, what i would do to made elves plausible?
1.High Elves - magic fortress unable to crack with normal weapon,superhuman strenghts and speed,magic armour and magic weapons.Thanks to that ,let say,100 elves could wipe out 500 veteran human soldiers loosing 3 or less.
2.Wood elves - strenght,speed,magic,and forest helping them fight.