List your favorite armies of 8 units here:
Elves:
4 archers(take hits, inflict light damage early on)
4 warriors(finnish of enemies, inflict heavy damage)
This army is very good at killing people, you will take heavy casulties however.
Undead:
3 skeleton archers (take hits, can kill some units)
3 necromancers (give you more guys so you win the battle)
2 death knights (you should still have 3 unique units at this point, there job is to rout enemies)
this army wins battles, killing is irelevent becouse at the end they have 2 standing units and you have 10