Why are Theurophoroi so weak?

[QuintusSertorius]

Peltastai are awesome, able to perform most roles reasonably well.

They most certainly are. You've got a skirmisher who can also perform admirably as medium infantry. I opened the Unit Compare and put them up against a number of comparable units. Both Camillian and Polybian hastati, Thrakian peltasts and Karian warbands. I would have thrown in Bruttian pezoi, but they don't seem to be on there.

Against the hastati, they compare pretty well against the Camillian ones, not surprising given how cheap the early hastati are. Not as good with the sword (by two points), but it's a better sword otherwise besides mass (slight advantage to the hastati) they're on par. More, but lighter javelins with a longer range. Polybian ones have better armour and morale, and an equally good sword, so the advantage vanishes.

Against the Thrakian peltast, higher skill, but their weapon isn't as lethal. Thrakians are slightly better with their javelins.

Uazali I think are a good comparison because again sword-armed medium-ish infantry. Almost as good skirmishers, lots of them, slightly better skill and slightly better defense overall. Not bad hastati-a-likes, though they don't have the morale of the later ones.

Get peltasts into a blacksmith and their weapon and armour bump up a grade. Get them some experience and weapon skill and defense skill, along with morale do too. Which puts them solidly into medium infantry range. Couple of chevrons and they're equal to Polybian hastati, yet available to almost everyone and not very expensive either.

Compared to Theurophoroi? The spearmen have better skill; though with the -4 vs other infantry that drops to a single point. Same lethality. Spearmen have 3 points more armour and a little more mass. Peltasts have more, longer-ranged javelins. Equal in all other respects.

EDIT: I've decided I need to give Theurophoroi a proper go, especially since historically the faction I'm playing liked them. Plus if they are weak then it'll make my battles harder. Not as line troops, mind, but to take the place of Keltohellenikoi as people flanking the centre. I'm going to ditch the classical hoplites for Keltohellenikoi instead. Not as tough or dependable.