Have you still not beaten it?
If you do start over, try building this army:
1 Praetorian
6 Legionaries (focus on dealing with infantry)
3 Triarii (focus on dealing with cavalry)
3 Auxilia
3 Auxilia Archers
3 Auxilia Cavalry
That's basically what I built my first time, except I replaced one unit of Triarii with Principes (oops... worked well when I was facing celts, but they got annihilated in CoM). Made it through CoM with that army on Normal, and only had to repeat 2 or 3 battles, and only one of those failed to be won the second time through. If my haphazard assembly of that army can crush CoM as well as it did, I'd imagine a planned assembly of the same would be immensely more effective.
In hindsight, my glaring mistakes:
1) Using even one unit that I didn't plan to keep permanently in even one battle. If you get rid of all your starting units, you have just enough to get your first Auxilia unit and start employing a squad that will be with you at the end on the very first level. That's what I've done on my new run, and it's working very well.
2) Getting the second and third units of Auxilia Cavalry and Auxilia Archers, and third unit of Auxilia way late in the game so they were low level. Considering how awesomely invaluable my number I units of Auxilia Archers and Auxilia Cavalry were in winning CoM, I'm next to positive it would have been a lot easier if I'd gotten them in blocks of 3 at a time instead of spreading them out. I'm doing that this time; got 3 Auxilia, 1 Praetorian, 3 Auxilia Cavalry, then 3 Auxilia Archers and THEN started building my heavy infantry force and it's working GREAT.
3) Using Hastati/Principe; if you're going to play CoM once you finish your Roman campaign, just give it up. They'll survive the first few opening encounters, and then quickly become fodder troops used to decoy the enemy, because they'll be 100% useless in a fight.
4) Not having a plan as to what upgrades I wanted and what equipment I wanted. Huge mistake. I paid dearly for the mistake of not getting Odysseus' bows and Sarmation Cavalry Armor until very late.
5) Not upgrading my Praetorian unit enough. Like I said, they're a deus ex machina unit.. once I realized my mistake and got them above thirty, they would
completely shred anything except 35+ level Helephants and shadow cavalry. I lost count of the number of times the day was saved by a Praetorian wedge slicing through the center of the enemy's strongest point and breaking their line.
6) Not realizing the best counter to Shadow Warriors are heavily upgraded and armored Auxilia Cavalry, rather than Heavy Infantry. Found this out by mistake when I did a last ditch charge into an advancing mass of Shadow Warriors and they magically managed to hold and stop ALL of them (with the help of Legionaries reinforcing their flanks).
7) Not directly involving my Legate in battle on the front lines as heavily and often as possible early in the game when he can get lots of points without dying. By using him like crazy on my current run, I had Quick Thinker, Strategist, and Leadership maxed out before I even reached the first Samnite War. He's already well on his way to level 30 and I only just started the First Punic War.
And finally, if you've got a spare $20 and enjoy your military history and tactics, get the
Byzantine Strategikon.
A lot of the tactics and deployments found in that book are directly usable in Legion Arena, and to great effect. First and only combined arms theory prior to World War II... can't go wrong with that.
