its good Saurus arn't too smart
I disagree with this statement 100%. Everything that I've read indicates that Sarus are extremely intelligent creatures. They instinctually have the knowledge of the best tactics when they're spawed. The reason they do not communicate as much as their skink counterparts is because their role is primarily combat and there isn't much to say about that, considering that everyone of them is practically thinking the same thing. Scar Veterans and Oldbloods don't have to issue many orders, especially on the battle field, because their Sarus rely on their instinct for combat tactics and timing. I'm pretty sure this is evidenced in the new and old books about the LM. Just because their role is to act as the best infantry the army (or nearly the world) has to offer and don't need to communicate to fill that role, does not make them any less intelligent than a skink. Remember the Old Ones spawned them for different reasons.
On an opinionated matter of the skink spawnings, I'd say that skinks that are spawned for a specific purpose spawn together and skinks that are to have two different roles in the Old Ones plans will not spawn at the same time. Basically, you won't see a group of skinks that are intended to ride Terradons spawned at the same time you would see a group of atrisans or scribes who attend to their Slann.