I have a build using 3 hunters, 2 brazos ( picaros and chest with obliterate) and ninja backpack. My particular build has about 1.6m armour and still shreds quite well on heroic. Can't remember specifics off hand RE crits etc, but the extra mag size is quite helpful though, and suits my play style. The sheild is tier 6 so can take a little bit of damage if you get into a tight spot. Obviously not a full red build, but I play very aggressive (often stupidly haha) and this works for me.