Somebody Please help me understand how to get past that damn hard Swamp Walker!!!

I dumped everything I had in that ultimate lepic build that is supposed to finish bosses in hope of it killing him. Farmed reactor and components with the required golden rolls, use an impact weapon with fire rate and sharp precision shot and all my lepic and weapon mods are maxed yet the damn thing frenzies every time!!!

Any tips on what i should be doing and how are those builds taking him out no problem for everyone except me???