You can only be kidding me. Even a BoD complete with eight OCs is hardly a threat to heavies. Iirc, an OC does twenty damage. Since it's "light" damage, it's reduced by half against heavies. That means eight spikes times ten damage = 80 damage. Now out of that, 95% is absorbed by the heavy armor. Five percent of 80 is 4. 4 damage is what goes through the armor and hits the player. A buddy with a welder can weld the other 76 damage that hit the armor faster than the BoD can reduce it. That means it'd take 25 shots from the BoD to kill a heavy, and that is only assuming he doesn't run right past it or gets medpacks. Heavy armor > BoD.
If your BoD or whatever you call it managed to kill heavies, those guys can only have been complete and UTTER smacktards, sorry to say it. And since smacktards < all, that is hardly an achievement.