Great thread, Paul. Some suggested rejoinders:
1. Weirdly enough, they count their numerical increase as proof of God's blessing and confirmation that God is using them. " As in the first century, today ‘a great number have become believers and have turned to the Lord.’ Although numerical increase is not in itself proof of God’s blessing, it does provide evidence that “the hand of Jehovah” is with his people." (WT05, 9/15, pg 8). "The earthly belongings of the King Jesus Christ have continually grown. Since 1971 the number of Witnesses has leaped from under 1,600,000 to a peak of over 3,700,000 in 1989. What proof of God’s blessing!" (W90, 3/15, pg 18).
2. Sure their "expectations" were sometimes awry. But in their eyes the fact that they realised and admitted they were wrong (eventually!) is proof that God continues to lead them to truth. "Things published were not perfect in the days of Charles Taze Russell, first president of the Watch Tower Bible and Tract Society; nor were they perfect in the days of J. F. Rutherford, the succeeding president. The increasing light on God’s Word as well as the facts of history have repeatedly required that adjustments of one kind or another be made down to the very present time. But let us never forget that the motives of this “slave” were always pure, unselfish; at all times it has been well-meaning." (W79, 3/1, pg 23). Bottom line: they're only human, but God is patiently helping them see truths when he thinks they're ready for it.
3. See (2) above.
In summary: Absolute hogwash.