Defenders are a great early game tool for clearing large biter nests in rampant, deathworld, and hive mind (smaller nests too but to a lesser extent as those arent as difficult to use gun turrets against) but nobody ever uses them cause they see military science required and get scared off (military science isnt even hard to spaghetti anyway so idk why people are so scared of it), once oil is obtained they are made obsolete by a giant flamer wall. now what happens if i dont spawn near any easy to access oil and need to kill some biter nests? defenders! seriously everyone really underestimates the power of these things, honestly almost on tier with flamers even with oil.
TL;DR: defenders are basically offensive flamers without oil and not a noob trap at all