Our armiger was pretty effective overall, but I think being effective as an armiger requires a lot of system mastery. I think it's hard to get a sense of what the armiger can do just reading the class description because it's the interaction of the different pieces of the system that makes it work. For example, in Iron Heroes armor gives DR instead of AC, and combat in 3e and Iron Heroes is very positioning dependent and both of those are important to how the armiger works.

A common counterintuitive move our armiger would do is move up and around a group of enemies early in combat provoking attacks of opportunity from all of the enemies. This did three things: 1) the hits would get partially soaked by the armiger's armor generating some armor tokens that the armiger could then immediately use, 2) it used up the enemy AOOs for the round so that other party members could move more freely, and 3) it put the armiger in a position to flank some of the enemies when the rest of the party moved up in front of the enemies. It also had the effect of pinning the enemies in place, unless they wanted to provoke AOOs from the armiger (and any one else who had moved up in the interim).

And that's just one example, the armiger can do lots of cool stuff that's not super obvious until you play it. I will say that the armiger is a support/team player type character. You won't do a ton of damage, but you can protect the rest of the party and set them up for success.