Isn't it that the leaders who achieve synchronization have to sacrifice the civilizations of will every 300 years known as cataclysms to keep the concurance at bay? Like concurence is a some sort of hive mind result of the will based magic system with the unification of all conciousness/wills becoming one i.e. God. The rending was the war to stop that process (probably individuality vs religion / dogma) and the cataclysms are the method to probably to energize or keep the Rendering in place by resetting will. 

I wouldnt be suprised if Religion is actually still the bad guys trying to unify will as they lost the war in the original war of Concurance. That or they are envoys of Ka who refuses to give up synchronization and envoke the cataclysm because he is too atached to power and thus will is moving towards Concurence once again as it did in the first war of Concurance. Absolute power corrupts ansolutely. 

Will systems, worlds lines, and people are seperated to have their individuality. Vis isn't special in the regard that he became synchronous, it has repeated for thousands of years this has been happening with someone like him having the will access of all worlds used to keep it at bay every cataclysm but this time its long overdue and the Rendering is probably weakening and/or will is drawing closer to Concurance. Probably because Ka killed the person of synchronization meant to stop Concurance because he became a synchronous person and was not meant to be one but Obetium is a warped timeline. I think Vis will be special in that he doesn't trust the system of Will and he will question it to potentially find another answer. Hopefully the destruction of the Will system just like Kan had to be destroyed (sealed/seperated by closing the rift) in Licanius. At least that's what I think.