I normally call tzeetnch the god of retards luck, it seems more fitting. Though gorgorgulaths plan was well made
How about a Chapter that returned from the dead? And the Emperor is immortal, he cannot be killed and he cannot die, and he may very well have even transcended mortal existence (courtesy of the Imperial Cult, no doubt, for as much as I disdain it).
A rotting corpse on a throne being fed psykers for breakfast lunch and dinner is NOT immortal. Hes just in a vegetable position until the Chaos Legions sever his head from his body, and then he will be just another skull on Khorne's bone mountian
And the gods are not different? Sitting in their thones demanding the pain and suffering of others in different ways. Atleast the emperor tries to bring order and prosperity
I have it on good authority that he very much is - at least in the sense that he will simply be reborn if "killed". Also, the Wolf of Fenris is correct, your supposed Gods are not much better, following your logic.
Unless that warrior is led into a grinder, or is forced to fight with another warrior and die like a barbarian, or is enslaved by Telepathy and told what to do as a dog, or outsmarted, or simply becomes a Pawn of fate. Tzeentch orchestrates Fate itself, you know? His schemes are what mortals refer to as "destiny." Something that requires far more intelligence than what the other Gods do.