I'm farily certain it was stated in the fluff that the emperor while unable to stop the vortex that took them was capable of influencing the pods in certain ways.Ehm Chompy you totally go up against fluff by suggesting that Empy had any control of where the pods landed. They all landed in shitholes, some worse than others. The only one landing in a place that could be called good was Roboute. Every Primarch was formed from the place he landed on. Remember the gods of Chaos spread the pods around mutating some of the guys (I'm just glad Alpharion and Omegeron didn't become one guy with two heads like an Ettin).
The geneseed of Leman Russ had some canine-things in them, I'm not denying that. But he was to be the Emperor's attack hound. He was mindless and singleminded which made him loyal but not endearing by any means. Though I'm unsure of how much that was from Earth and how much that was from the warp. I mean from the pictures I have seen of him, he seems perfectly human to me, without even the dog-nose of Goofy-fame.