Anything corrosive works well on them as already previously mentioned in this thread. When I ran through it with my Axton, a corrosive Interfacer + Bee + Slag absolutely demolished them (you really don't need the Bee, but it just helps drop them that much more quickly).
And don't use explosive weaponry on them as someone suggested that you should give them a go in this thread. Armored targets already resist explosive damage, and to top it off, in OP 1-8, enemies have a varying innate damage reduction to all sources of damage, so you really don't need to be dealing lesser damage than you already are. Not saying that you couldn't demolish them with a DP Harold or something (because you absolutely can, since I've done so myself), but all I'm trying to say is that you'd be better off with a corrosive weapon.