For this method to work you need to suplement it with either this Fluctus build or this Mausolon build

Difference between 2 weapons is

Fluctus - CAN'T destroy Orphix (well it can but it's very hard to find perfect spot) can shoot trough walls/objects easier to destroy Orphix Resonator but requires clicking fire button rapidly

Mausolon - CAN destroy Orphix and have more DPS but requires line of sight with Orphix Resonator to destroy it while its autofire (hold fire button to shoot)

And here is the trick personally i go with Fluctus cause i destroy more resonators and enemies trough walls/objects than "Orphix'es"

For Orphix himself i just use Guard Mode (press 4) and destroy him with Arquebex

TIPS

• HEALING -> Vizier Predasite with mod Iatric Mycelium (you get it with that Predasite) leaves trail if you step on that trail your Necramech will be healed
• Orphix Spawn rotation (1st 4 can be A B CC or A B C B or something else) then stays with A BB A CC repeat so in other words if spawn location occurs and it DOES NOT repeat but just switches to next one then this was spawn A
• And just follow this pattern START (1st 4 whatever) then A BB A CC A BB A CC.....and so go on
• After few runs with mod setup from above turns out you become kinda immortal as long as you keep your Storm Shroud ACTIVE (making Combat Discipline useless and it allows you to sustain yourself no matter who you got in your squad and what they do)
• [Combat Discipline] Aura works on Necramech except your own so when you kill WHILE IN Warframe all squad members Necramech (or in whatever they are in at the time) are healed except your own Necramech
• You can't avoid that animation after you stop sliding but you can negate it by jumping at the end while still sliding
• Activating Storm Shroud (press 2) while getting attacked from many sources is good idea since you get 3 seconds invulnerability time frame in which all incoming damage is multiplied into Storm Shroud's HP
• IF you are taking beast companion (for example Smeeta Kavat) with you i suggest going with Inaros (throw into him all HP/Armor mods you can find) + Link Armor + Link Health on your pet since it kinda won't let him die
• If you wonder about getting [Necramech Redirection] instead of any other mod from above well i did i replaced Thrusters and even so i don't feel like loosing anything i didn't also felt that i get anything so totally not worth it's just wasted forma (IF you don't look at your HP then 2x shields won't give you anything you need to keep Storm Shroud active)
• I tested Necramech
  -- Augur (not worth it refills like 80 Shield)
  -- Aviator (very cool if you want to jump like monkey sacrificing Guard Mode)
  -- Blitz (not something great but considerable jus for fun)
  -- Deflection (even so it's faster it's too slow to be worth of a mod slot)
  -- Drift (you don't hover long enough during Orphix to make this mod worth it)
  -- Hydraulics (in 1 corpus tileset it helps in any other tileset it will be your enemy)
  -- Rebuke (it's like you fart after your shields go down and you hope to make it any combat difference)

How it works

• Shoot trough walls/objects all Orphix Resonators (best idea is to aim little below red waypoint)
• Go to Orphix and stand in front of him just so his eye is visible
• Go into Guard Mode (press 4)
• Fire until it die
• In meantime activate Storm Shroud (press 2) to protect Necramech from damage (just keep it active)
• Repeat
• Enjoy

I just want to point out that at Orphix Venom Endurance killing 36 while using builds included here + method from above WITHOUT paying big attention to Storm Shroud but just checking it from time to time i die like 3 times around 25+ Orphix if i pay attention to Storm Shroud i don't die at all

And so far with random squads i am main damage dealer
When my Necramech dies they struggle to do constant damage seems no 1 is prepared for this battle and 99% of them try to kill it with archgun instead of [Arquebex]

This build is interchangeable with my Voidrig Necramech 3D build

Can't see Crosshair?

Google Custom Desktop Logo
All you need to know about it is on youtube

Settings > Location > Display AT Location Offset
Location Offset > manually change X and Y and either press tab or enter to see the result

Whatever folder you choose it will cycle trough all images in that folder so you can make flashy crosshair link to some crosshairs https://imgur.com/a/4O3OB5F

Put all crosshairs in Custom Desktop Logo\System\Images\Crosshair
That folder does not exist so just create it
Then just right click Custom Desktop Logo icon in tray area and choose settings then choose image folder as that Crosshair folder

How it looks 
https://imgur.com/a/s4v5EoP