Why do certain players think that some factions are underpowered?

[Treverer]

To fight when you are on the brink of disaster and have (according to computer) an impossibly thin chance of victory, and yet prevail, that is what I find thrilling.

Yep, won a battle at Taras with each one levy hoplite, hoplite (both no upgrade, no chevrons), archer & slinger unit (both upgrade and one chevron) against ... ehm, hmmm, ... three Romans: two Reserve Skirmishers (they weren't my problem at all) and one Triarii (having 2 or 3 chevrons & amour upgrade). Well, my loses were beyond good and evil, but in the end the Triarii routed. Yes!

And now: