for battle hammer it means you can start demoralize enemy at 205-280 armor (based on min-max damage), while w/o fearsome it will happen at 65-140. So differrense is ~2 hits more for same effect. For 300 armored enemies you will need 3-4 hits to the body instead of 5-6. Sorry, i didnt calculate it for some other weapons.
Well, Im sorry I don’t know why you have to take hammer for example.
Actually hammer has at least 10hp damage guarenteed. That means with fearsome demorale is guarenteed no matter how much armor opponent has. But hammer is just a especial exception, fearsome with hammer work well doesnot mean fearsome not weak.