One of the biggest facts that got me thinking many years ago is the difference in how many become witnesses each year compared to how many people are born in the world each year. It seems that there are approximately (very roughty) 200,000 people added to the WTS each year, give or take. That's about how many people are born each DAY on the planet, give or take. Yes , the percentages may show an increase for the witnesses, but look at raw numbers.
According to http://www.worldometers.info/, I figure there are about 74,000,000 more people each year on the planet. If the witnesses convert say 250,000 people each year, then that is 73,750,000 more people Jehovah has to destroy each year that armageddon comes.
I was always taught that if Jehovah had brought the end in 1914, 1975, etc. (take your pick), then look at how many witnesses would not have been gathered. I say look how many more people have to die for every day the world goes on.