yes but i think it seems odd that we've only heard mention of two different primus's, so maybe overall command could fall to a primus for several legions

That does seem probable. So far we know and understand the general hierarchy of the cabal but the actual exact amount of power each rank has is unknown to us. Most assume that a Primus controls one entire legion based on the Roman military. But maybe bungie could go a different route. Here's a personal theory I just thought of as to why we haven't heard of the other Primus' and why we only killed two but the cabal "didnt have any high ranking officers" left. My theory is that most legions we see in destiny are support legions. Here's how I see things. The cabal scouting legions operate in two distinct categories: Ground forces and Air forces. Each category has a Primus that controls all legions under its command. The Primus then chooses a legion from his category to command personally and leaves his Valus' to command the other legions. This is similar to how Ceasar structured his own legions. So going by this theory the Dust Giants, Sand Eaters, Siege Dancers, and the Blind Legion are all ground forces. While the Skyburners are the air force. The Primus of the blind legion is the Primus for all ground forces and Valus Ta'aurc and all the other Valus' control the other legions. This explains why the Siege Dancers have a Valus commanding them.

that makes sense, i thought that maybe the sol invasion force was commanded by a primus, and the skyburners came later to shore up defenses and help with the stalemate the cabal had seemed to have fallen in