User blog comment:Blueyhale/How do World Eaters get around without psykers?/@comment-26066352-20150827220714

They definitely use human psykers for navigators etc, of course they can also use mutated individuals for certain unique methods of travel and communcation. For combat they wouldn't need psykers for their combat abilities because their strat is to suicide charge with chain axes (10/10). As far as daemon summoning goes I'm not 100% sure.