Tips and tricks to build:
high DEF on ancestor mod.
with 210% DEF am and this build should be somewhere 335k def.
ajax can buff own DEF, so 300k should be fine if not you can change "holding the line" mod to "shield conversion (def)" mod.
Guns:
Mobbing: Eraser
Wall Crasher: Thunder Cage good to go or use Eraser or Shakles.
Skill Rotation (important)
1,2,3,4,1,2,3 in succession then hit a enemy with a skill then shoot it.
time to time (depents skill duration) you need to do 4,1,2,3 and hit enemy with a skill and then shoot it.
by hitting enemy in 1st skill renegates ammo per tick.
by adding "Compulsive impact/high-power rounds" modules to Eraser and piercing light, per tick you get even more ammo.
Ancestor mod:
for a good rolls, you need:
2+1 format. that can give even +200 DEF.
Priority:
DEF
good ot have:
Range
Duration up
non-attr boost
Tech boost
for a good negative:
dimension (boost and modifier)