Armored Golem does... 30 shots at 5000 damage a piece every 2 seconds. If the golem was spreading out his attacks across 30 targets, I can imagine why it might seem like it's not doing much, especially on high tier ships that commonly have 100,000-300,000 health. On the other hand, the golem has an absurd amount of health and no weaknesses to any attack types, so it probably would take a long time to die.
I found that using golems offensively like that doesn't work very well because especially on MK III and Mk IV planets what ends up happening is that the AI reinforces faster than he can kill them (they give a multiplier to AI reinforcements), which usually results in a beat up golem, a lot of wasted AI progress, and no real discernable progress made against the AI.