No, i have the same problem.
English isn't my native speech, and although i can speak it quit well, i can;t write it correctly. This way, i use whole different words then i would use in my own language, just because i don;t know the apopriate word.
You'll see the sentence aboe is filled with grammatical mistakes, and i didn't do it on purpose ^^
This way, i also have a feeling that when i write, i just can't...capture the right feeling of a dialogue, like you pointed out.
So i just keep the dialogues as simple as i can ^^
"I think the Devil ****s Dutchmen."