It seems that in the past year there have been an unusually large number of Gedolim that have died. Granted eveyone’s time eventualy comes, and my perspective is a bit limited. Assuming I am right, that this has been an unusual year in this respect, what do the sources say about this phenomenon and its message?

I have no idea if this year has been unusual in the respect you mention. Each Tzaddik is a blessing for Israel, and when he or she is niftar it is a great loss, but also a kappara (atonement) for the people. Sometimes we are in need of such a kappara more than we need the presence of the Tzaddik. We have no ability to to view HaSem's plans in this respect, but each Tzaddik has a unique contribution to the world, and presumably HaShem knows when the contribution has been fulfilled.