[BigDaddy]

Wait, you use Velites AND Principes right? I pretty much insist that the cheapness of Velites makes them awesome. They're my most hired early legionaire unit. Late I drop some standards in all my provinces to beef up the defenses.

It might be that you are right though, I ussually pick the emerald guard because I've had good luck with their durability, especially getting them to hirer experience levels without wounds.

Assassins have a nice precision and are nice to carry x-bows. Adding a few to a force is similar to sending a mage.

If you're willing to make a castle to hire assassins, then it frees up some time to research construction.