Burster (boss of Breach Broods) and Dreadful Disruptor (boss of Reality Reavers) are rare bosses and not because of it's rarity in fact, but simply nobody checks it. I can't even say what is the mechanism of these bosses. I can only assume, that it is similar to the Mahatheb/The Mean Masher or The Manhunter system.
That's why it is hard to say what is the loot of these bosses. All I can say for now is - "I don't think so".
My friend during making bestiary on weak sparks killed two Bursters during 10 minutes, If this boss is so easy to meet during hunting, then I think it is even less possible, that they drop anythig rare.