I think the dictation is required you to listen very carefully.
And every if you listen carefully, you don’t always catch everything.
And sometimes he hear very badly and feel shame, but you shouldn't, because you heard very well.
But it’s good way, because then you develop greater understanding of the language.
Because when you are doing dictation, you are not doing literal English.
Because people don’t always speak literally.
How you speak, I suspect the same in Japanese is not the way you would write it.
So the dictation is good way.
But you need a lot of effort
Most of people don’t have time for it, I think.
But you are going to be a journalist, something like that, or you are going to be a writer, then it’s the most effective way.