Phoeny has trouble in iron, as it should, since its the 2nd best boom civ, and 2nd best overall civ in the game.
It gets AE's, scythes, EA's, and full tech priests. It gets a great navy, but it lacks any good *defensive* unit, aside form the priests. The proper strategy for a good phoeny military attack is as follows (at least in my experience):
-Naval dominance. Built hundreds of docks, pump out fishing boats, triremes, cat triremes, and later on, if you have the wood, juggs. Naval dominance is extremely important to a food heavy military like phoeny's, and fb's will rake in tons of food.
-Defensive ground based positioning: initiating combat with phoeny is a bad idea. The lumbering eles take ages to get to the battle scene, and when they do there's a priests waiting for you. In general, it'll take you a long time to move a co-ordinated army from one place to another. So its better to keep the scythes back at your base, with the AE's. Phoeny is not a fortress hacker. Of course expansion is a must. AE's, EA's and scythes are your main force.
-Centurions/phalanx: this is only in theory, but an opponent will wish to counter your scythes with tougher hand to hand units. Take some cents along with you, and they'll catch the opponent off guard.
Getting juggs may seem like a bad idea, but on a continental map, with lots of wood near the shore, you can deny siege civs the wood they need. Then you can wear them down and eventually win/draw.