From what I understand, the portions of OT that are encompassed in the Bible refer to a Canaanite God (El) after the Jews kind of converged on a single deity to replace various local ones in an attempt to "unite" a bunch of semi-nomadic tribes that all had their own tribal god where "El" was a common overlord (kind of like Zeus in Greek myths).
Christians of various sects ~200AD were convinced that God walked the earth as Jesus. They integrated both Jewish and Greco-Roman lore into portions of what we now call the New Testament. They also got together a bit later to again, remove what didn't fit into a single narrative to unite various Christian groups with various different viewpoints in order to consolidate political power (Paul's quote alludes to that fact when he says regards Peter, Cephas and himself having different viewpoints on the deity and trinity of Jesus).
The JWs translation actually accepts almost the entire portion of scripture that modern religions view as canon except they reject certain portions and will even remove entire verses if it doesn't fit the theology. http://www.catholicapologetics.info/scripture/translations/neworld.htm
All in all, the JW translation is unanimously rejected by scholars as being incomplete and incorrect with a heavy bias towards their own theology. If they were honest and as they claim they do would go back to the original translations, not only would their bible not miss certain portions, it would add in several more books and actually be on the forefront of accurate Christian text translations. They would also have to explain the trinity, deity of Jesus and why their Bible has even more conflict than a "regular" translation, at least they would have a standing when they scold other religions for changing or leaving out portions that don't fit their theology.