I have not played EB for several months, so I'm not really very aware of the statting procedures, but the heavy Persian archers are supposed to be at least as good as the Mardians, and with superior armour rating, making them the creme de la creme of foot-archers. They do have studded leather, and a helmet, as well as a functionable acinaces to do the cutting, so they should not fare all too lousy in melee. At least that was the intention

The reason why I and so many others favour the Iranian archer-spearmen, is because of the killer combination of cheap recruiting and maintenance costs, and the fact that they can kill horse-archers better than any other lightly armoured infantry. Put them on the down-ward slope of a hill and watch them turn light cavalry into dead meat. The enemy will think "Damn if I do, and damn if I don't". With them around, you don't need to chase light cavalry ever again, and if the enemy horse are enticed to charge, the spears will hold them off. They also provide an adequate line to hold against enemy infantry so that the cavalry hammer can smash them. It's all about philosophy. They won't decide a battle, but they'll do the shit work for you for a little cash

In siege defence, they are demi-gods. Once you give these guys some chevrons, I kid you not, they will rule. It's like laughing in the face of the craptacular Sotaroas. In fact, these guys are so important to me in a Pahlava campaign that I go first for the provinces that may get me these so I can have my back somewhat safe. All I miss is that enigmatic "Achaemenid'esque" wicker pavise to the front, but that is easily solved by recruiting a Parthian spearman, for every two contingents of the Iranian archer-spears, and stretch out their front.