Prodromoi are indeed weak. In my Mak campaign I thought they would deliver a good punch and charged them into a battle. In a short time they've started to drop in numbers and I had to retreat them.

I think they are quite similar to Roman bodyguards in their performance. They are good for rear charges, chasing routing troops or routing wavering units. However they'd be decimated in prolonged melee against most infantry and most cavalry (except may be the lightest and unarmored).

Their advantage is the price and very wide AOR for any Hellenistic faction.