ff Brass layer
One of the reasons for “fake” sounding orchestral mockups is the overuse of the ff-layer on brass samples. Very often you get to hear for example horn lines that last for a minute and are all played at ff without any rest or natural phrasings. In reality that would not be possible just for stamina reasons. Especially that “brassy buzz” sound is not possible to be played over a long time. Often, even though the mock-up might be very well produced that artificial writing attitude for the brass takes away a lot of the realism.