They are just like gnomes, 5 gnomes without any training and gear will also have problem dealing even with golems.
But if gnomes will be able to repair them after death, they will become pretty much safest way to defend: increase their skills in training without any chance of losing highly trained unit in battle. It will also create a good way to make use of metal from goblins. May be decent way to defend at ultra high KW without "cheety" feeling of custom traps.
But if we will be able to produce them indefinitely, especialy without KW increase, they will definitely be overpowered.
They are stronger than unarmed gnomes. They can have a body of steel that withstands mant attacks, and have punches and stomps that tear bears apart. So, pretty overpowered.
They are amazingly expensive. I do have 5 "Punchbots", wich I used them in the last goblin invasion and it set me back 50 steel in repairs. The same goblin invasion gained me 120 "meltable" parts, resulting in maybe 200 slivers, which results into about 20 bars of (overpriced) steel. The exact numbers are hard to come by, but most parts only yield 1 sliver, and those parts are most common (helmets and breastplates tend to get obliterated) - I also get some iron clad goblins in the mix every now and then. Granted, that battle was one of the more "smooth" ones because I had 5 extra soldiers that really held their own. But I am now struggling to keep up with the steel demand where I was "in the clear" before (and also winning the battles).
Granted, they only have about 40-50 fighting skill, and about 10-20 dodge (so I expect greater things from them) but they probably will always be expensive to repair. Breaking armour costs you nothing at all if the gnome wearing it survives the hit. Granted, I prefer a damaged/destroyed automaton over a dead gnome - but you need to train up automatons before they get anywhere near feasible for combat. Just like gnomes, tbh. Which is fine. They should in no way be a surefire, out of the box way to win vs. the enemy.