I don't think armor needs to be buffed across the board, but I do think certain ships need a great deal more of it. For the most part, cracking a ship's armor is something you get a brief opportunity to do—when it's overloaded, when it's venting, when it turns to block a missile volley. Some ships always have their armor exposed, though. For something like the Dominator, which has ample PD covering its weak rear and strong armor to begin with (and shouldn't be flying around without escorts to keep AM-blaster-armed frigates anyway), that's fine; for something like the poor Buffalo Mk. II (which is underarmored even compared to some frigates), it's not. A ship without shields needs something to compensate—if not Hound-like speed, then stronger weapons or tougher armor.
Worth noting: the way armor works right now is a little difficult to understand, particularly for a new player who looks at a ship's stats and just sees a single number for armor. For example, it might seem like applying heavy armor to the Buffalo Mk. II would double its defenses (200 to 400). In reality, that improvement to armor will halve the damage dealt by only the weakest weapons (e.g. the mining laser); it will cut the damage of a mid-range weapon like a pulse laser by a third and barely dent the damage of a strike weapon. All that is fine mechanically (I actually like the system right now), but I hope that somewhere down the line there'll be a thorough tutorial demonstrating the effect of weapon types and armor rating to the player.