well It seems to me that when using praetorian cohort they
a. won't break that quick
b. have a lot of defense and offense
c. are almost completely healed most of the times after battle.
I've had a case where 54 of the 61 casualties are healed.
An early leg. cohort has an advantage against cavalry, so put them on the flanks, but support them as they are less effective against other infantry.
On the cavalry side I am less happy :
if I charge an two unit group of cavalry, consisting out of a roman cav unit and a cav. auxillia group, head on into an equites (pre Marius!) unit (which is trying to flank my infantry), then the Equites are mopping up my two units.
How do you explain that?? a heavy cavalry and a light cavalry beaten up by just 1 light unit...
+ charging head on into an infantry does not work well either, they get mopped up. Better it is to have another infantry unit to engage, and then rush in the cavalry.
I've found that especially Velite Gladiators are very tough against Cavalry...
so try to use these one the flanks also...
+ trying to kill a general is tough, very tough.
Most of the time it takes me a unit of infantry (heavy) and 1 or two units of cavalry to pin them down.
If they find a hole, then you will never see them again if they run (are just tooo quick to catch up)
about long range : the experience I've had was that archers only can kill the lighter units in an efficient way.
Onagers are doing much better in my opinion + you can use them at a much longer range ...
"Horum omnium fortissimi sunt Belgae" (Caesar - De bello Gallico) - of them all (all Gauls), the Belgians are the bravest