just came back and glad to see the 1.0 unit balancing is SO much improved now. We are looking more and more like roma surrectum now^^, maybe it'll only be 1 more year for everything to really get polished and become legend status.
Comment on the OP's question also, the empire focused on different types of units during different reforms, early triarii are from the spear/greek-like fighting style during the camillan era, and likely spear units were generally more widely trained/available and easy to obtain. after polybian romans mostly went to gladius and spear units are much more rare so prehaps their production/maintenance isnt as "efficient".
also, one of the main things the reforms did for rome wasn't unit quality but unit availibility, in roma surrectum, polybian legions were only available to train in italia and only after marian reforms can you train legions outside of your starting area, this severely limited your ability to expand to distant areas prior to marian reforms, which was exactly how

went down in history. hopefully one day this will be implemented in DEI too
