Yes. The Roman Onager can loose multiple rocks for a wide area effect. This tech can let Sasanian archers shoot 5 arrows at a time. Ships can volley several projectiles at once. Is there an Issue or Pull Request for it? 

I feel like we were able to do this with CWA back when it was historical.  We got Ele archers to shoot 3 arrows, one for each archer... but doesnt seem to work anymore.  We had to turn them into "building" AI so they were unable to capture, and then it was when there was random fire and not focus fire.

That is probably beyond my time/abilities but I know it has been discussed. I think it would be a great opportunity to enrich gameplay (multi-projectile siege, unique units, ships perhaps).

EDIT: Fixed. It was these lines:   range/ and stable/ were missing after I moved those techs to these respective folders. 

Parthian tactics is un-researchable even after researching Archery Tradition and Advanced Cavalry for Xiongnu and Scythians.