We have to quantify the risk of the project once again because of the faulty descision we made by the neglect of duty. это звучит нормально?

It depends... There really isn't a simple answer that is a 'one size fits all.'

It's hard to explain, but what I mean by that is that there are different tones for written pieces that isn't really meant to be read aloud, and for pieces of text that are.

This one is grammatically correct in written context, and it would also be correct if you added a comma to it.

Basically just access whether or not if what you're writing is to be read aloud or not. If it is then read it aloud, if not then just make sure it's grammatically correct in written form.