Use auto_win, always. Unless you are on easy battle difficulty auto resolve is horribly rigged against you. It's pretty common knowledge that it's messed up, so just save time complaining and use auto win if you don't want to manually command it. Auto win will give you generally 10% casualties with relatively equal force which is pretty close to my usual numbers versus a strong foe and saves a ton of time. I use auto win liberally since it's really no fun trying to play along the rules when the rules are really messed up against you and the only reason you're auto resolving is to save time. The only time it's bad is when you have an HA army, but then you get more unit xp than normal battles where you don't lose a man.

And I challenge the Gestastae claim as well. The Thorikitai Argyraspidai are more than match for them: one on one I don't know but in terms of holding the line and forcing a gap, and surviving missile fire, the TA are well above them. Frankly a lot of infantry units are better, examples being veteran/praetorian cohorts, argyraspidai and the other elite phalanxes, and maybe the baktrion and the other successor agema? All of these units don't get totally rocked by skirmishers and are able to force a gap and exploit it much better (at least the non-phalanx).