Drew, this is a subject close to my heart.
Bottom line.
There were 3 main classes by Rutherford's time:
-The Jonadab class/other sheep who were not anointed, who were 'men of goodwill' - still part of Satan's organization or the church system, but didn't sympathize with it (sighing and groaning, etc.) and who would be blessed on the earth.
-The secondary heavenly class, the great multitude - spirit-begotten, but somehow negligent in their faithfulness. Therefore they would be tested during the great tribulation, barred from being the 'royal class' but still serve in God's heavenly temple.
-Those of the 'high calling,' the 'royal class,' the 'Christ/Anointed class' who would be joint heirs with Jesus as king/priests.
What essentially happened was the Jonadabs/other sheep (who were NOT Jehovah's Witnesses, but companions or associates) got merged with the secondary heavenly class (great crowd) and became an earthly class in 1935. This was surprising since Rutherford was adamant only in 1932 (Vindication III, p.204) that the great crowd WAS a spiritual class.
The two-classes of Christian doctrine is based on 1914 and the old view that the sheep and goats were being separated from the time Jesus sat on his judgment throne in 1918. The earthly class could not appear before 1918/19, according to Rutherford. It is well worth getting hold of the 2 articles in the August 1935 WTs that explains Rutherford's reasoning behind the whole deal. PM me if you can't find it elsewhere and I'll try to send you the scan (it's a large file).
But if the prophetic significance of 1914 isn't true, and if mankind is not yet being separated (and JWs no longer believe this is the case), then the question is, WHERE IN THE BIBLE CAN WE FIND ANY EVIDENCE OF TWO CLASSES OF CHRISTIANS IN THE FIRST PLACE? Once the JW view of the end times alters, the two-class system can't be tied to it anymore. So where can we find reason to make a distinction between 2 groups of faithful Christians?
Hope this helps a little.