I am comparing Cohors Reformata (the standard) with Evocata; and Evocata with C and P Princeps

I think the professional marian soldiers should have more attack or lethality because I don't see any good reason to train evocata. They shoud tire very fast (cause they dont have the good stamina) and has a litte more defence. I think this defense value will mean nothing because they are going to be tired when still running for a charge, and tired soldiers die very very fast.
I think the only way to get advantage with evocata shoud be at a defensive city battle in the guard mode.

How can I change the attack value?