EB1: Phalangitai Deuteroi can be used as decent defensive infantry, well able to hold their own against most enemies provided that the enemy is attacking from the front.
EB2: The phalangitai may lack some of the esprit d'corps of the Makedones with their chalkaspides, but they are nonetheless a disciplined body of pikemen, stalwart when holding the line.
The Phalangitai Deuteroi are wealthier members of Makedonian or Epeirote society than the majority of peasants, but are still not in the class required to be considered Pezhetairoi (voting property owners), yet they can afford better equipment than their poorer taxeis Hoplitai brethren. They are armored in good Phrygian helmets, quilted cloth armor that can dampen the effects of missiles, and are armed with the dreaded sarissa, a six meter long pike. They are disciplined enough to hold a line well, and as property owners, have a lot to lose if a battle does not go their way. They can be used as decent defensive infantry, well able to hold their own against most enemies, so long as that enemy is attacking from the front. They are still vulnerable to missiles and flanking attacks, though not as vulnerable as their less wealthy compatriots. They are more disciplined and better motivated than their Asian or Aigyptian counterparts in the armies of the Seleukeis or Ptolemaioi.
Historically, the Phalangitai Deuteroi were only used during periods of extreme need or times when Makedonia was invaded. They represent the lower end of the smallholder class, and as such, are the primary food providers of the social order. They were used only rarely, usually during invasions. They did give a good account of themselves against the Galatai and Thraikes invaders, but were found wanting as the armies of Philippos V and his son were cut down by Romaioi soldiers.
Phalangitai Deuteroi form the backbone of every early Makedonia and Epeirote armies.
They are relatively cheap, numerous, and quite dependable. They should be used to form the backbone of typical Makedonian and Epeirote armies, especially at the start of the campaign. As with all pike units, facing enemy units that occupy higher ground and fighting in forests should be avoided. In both cases, the effectiveness of the pikewall is substantially hindered and thus makes their deployment even more impractical than it already is.
When used properly, Phalangitai Deuteroi can work wonders while sustaining minimal casualties. As long as the flanks and rear of the phalanx are protected and the terrain is relatively flat, the Deuteroi can keep the enemy in check and slowly grind their numbers down (effectively lowering their morale) while you outflank the enemy. Their effective deployment in strategic locations during sieges can also hold a huge army off with just a few units of Deuteroi, as the narrow roads in towns and cities make it impossible for the enemy to outflank them.
Like with all Makedonian phalanx units, there are practically no units that can penetrate their spear-wall up front. There are only a few exceptions like very heavy shock infantry (i.e. Thorakitai Agematos Basilikou), whereby they manage to break the phalanx in the long run. Other ways to break a line of Deuteroi up front include deploying siege engines, using very heavy cavalry (i.e. Hellenikoi Kataphraktoi) to charge into the spearpoints and, of course, using higher quality phalangites. All of these factors should be taken into account by the player who decides to use Phalangitai Deuteroi in his or her armies, in order to get the best out of them.
Below is the AoR (Area of Recruitment) of the Phalangitai Deuteroi (Makedonia and Epeiros only):