In answer to your question, I did a little digging.
Not being a specialist in either Middle English or Greek ( though I've spent time at both modern and ancient from time in the country and time with texts) I would say that we have digressed more from Middle English than the modern demotic Greek has from the Koine.
In fact, I am not sure that a Greek version of the NWT exists.
But still, here is the notion that New York based translators working from a collection of English translations add a theological insertion here and there and process it all back into passable Greek. What does this foreign intrusion provide a Greek Orthodox Christian with his own Bible already notated by nearly 2000 years of commentary.
In English, the NWT does not retain the language of the King James - and I don't mean that as a compliment. Unless a new edited edition of Canterbury Tales were written for a comic book, an effort would be taken to retain the verse.
It does not devote much effort toward the original OT verse. The verse and meter were there in the original Hebrew, but there is no grasp of it in the NWT. How was that faithful to the original?