Undercover, those "big 3" were the ones that were important to me when I was a believing JW. I remember going out in service and I LOVED to talk about the Trinity. I had dozens of smart-@$$ comebacks for Trinitarians (who was Jesus praying to? was God really dead for 3 days? who resurrected him?, etc.). It was too much fun.
I think these "big 3" doctrines are a large part of what keeps some Witnesses in the religion even if they see issues with doctrines, failed prophecies, corrupt leadership, etc. They say that nobody else is right. I actually agree with this statement--if you remove the word "else."