Executioner is great for dagger user. This and Full force.
Give man a Scramasax and enjoy free armours. Especially great against heavy armoured humans but when you start on hard you can use spam of knifes to get free armour.
I actually think that knifes and daggers should have difference in skills.
Knifes are more for cutting and slashing when daggers are more for stabbing.
With good character you can kill heavy armoured man with two stabs and keep his armour.
Obviously work not so good against orcs.