Board Thread:Warhammer 40k General Discussion/@comment-4851119-20140118095944/@comment-3258762-20140121173211

Neithan, I'm not sure you know anything about the Thunder Warriors. They're explicitly stated to be superior in combat to Astartes. It even says so in the introduction to their article on this wikia: "Wrought to be living weapons, the Thunder Warriors were known to be physically stronger, more savage and more potent in combat than the later Astartes, though they were not as long-lived."

Next, stasis has a debilitating effect on the mind each time it is used. For such unstable warriors as the Thunder Warriors, that would have been a catastrophy.

And I'm starting to wonder about your knowledge of the Remembrancers too. They never educated. Remembrancers were artists and writers that chronicled the deeds of the Legiones Astartes to serve as propaganda of the greatness of the Imperium, they did not educate any Astartes.

The Iterators, who might be the ones you were thinking of, has only one known occurance of educating an Astartes, that being Kyril Sindermann serving as an intellectual mentor to Garviel Loken. Iterators were meant to be diplomats to the conquered people, who would, through amazing speeches, make the populace feel as if they had been liberated, not conquered.