Your test actually yielded very, very accurate results. If you'd care to read about the Goidilic units in the Eleutheroi section of the unitpages on the website; you'll come across some fellow of which a historical source tells us they were so powerful that they had destroyed a quarter or so of an invading army (quite large one at that); by the time the other forces reached the fight.

Now that unit is a somewhat lighter copy of the Vasci original; and the Thorakitai Agematos Basilikou is an exact copy of the Vasci. Those Vasci were among the tribes to hold of & beat Romans very, very, very often. They are the absolute zenith of heavy infantry know-how back then -- outfitted in the very best equipment the entire Western world had to offer; recruited from among the best and fittest within the royal guards.

Such things cannot be said about the Praetorians. Actually; Praetorians existed even before Augustus: they are the guards of the tent of the chief commander of the army. As such they are chosen because of their comparative strength as soldiers; but most of all because of their unquestionable loyalty. So there you have it: the best equipment the Roman state has to offer (which isn't particularly good - compared to what you could get in Celtic & Iberian cities; or from the smiths in Syria) plus soldiers who are more loyal and have greater skill at arms than your average back-bone soldier. In the AS they'd have been the Argyraspides based on their skill at arms; and the Royal guard based on their loyality.

But they'd not have been considered good enough for Thorakitai Agematos Basilikou....