What makes their durability so shotty? They like the avengers armor that was also part of that fight got torn apart by extremist heat. I'd give them all round about durability of ironman 1 or 2 armor.
With that numbers plays a big role here and brings avengers ironman down. The house party crew will be blown apart by the weapons such as the missle that blew up the leviathan that hulk punched and the lasers but still the swarm of suits all focusing on him with repulsors and unibeams of their own nevermind whatever specialized equipment they have all used to pound him into the ground.
The suits in IM3 toppled like dominos at the hands of 3 Extremis f**ckers. Something Thor was unable to do to the suit used in The Avengers. See where I'm going with this?! Plus, Jarvis would have to operate most of them, who has proven a lesser operator than Stark. So, the way I'm understanding it, it's Avengers Stark vs. IM3 Stark.
unmanned armors are supposed to take out Tony stark? No. Didn't Tony give us enough proof that unmanned VI can't seriously touch him in Ironman2? Tony uses his exp and actually completed and functioning armor and lasers the crap out of them turning them into the fire works show for the next stark expo.
If not then he takes them out for a game of tag and leads them in circles as he picks them off.