So I've been trying out the new Apocalypse difficulty, cycling through different challenge modes and different builds, trying to figure out what works best, and finally had some luck with Angel of Light Travel and a Survivor build.  :)
The early game was pretty harrowing, but started to come together when I got Angry MoFo 3.  AoLT doesn't let you carry around much in the way of healing opportunities, but the combination of Survivor and AMF helped mitigate that, and I think the AoLT speed boost was a big help in just getting around the levels quickly, before too many enemies revived.
Mid to late game was carried by a strategy suggested to my by Sylph of using a sniper rifle, along with an auto-repairing helmet with aim assist, and cover master 2, which allowed me to get +100% crit chance on every shot against any enemy where I waited at least once beforehand.  That, combined with AMF3 allowed me to do devastating damage to everything, with just a few bullets, including archmedusae and archwarlocks.  (Sadly, I lost the helmet when I got surrounded in a hunt level on the second last level;  I had to use a handful of grenades to get out of that situation)
The sniper rifle was important for ammo conservation, since AoLT obviously doesn't let you carry much, (I had another A! game come to an unfortunate end due to running out of ammo, so I wanted to be better prepared this time) and for a good chunk of the early game, I had a JAC .44 as a backup in case dangerous things got too close, (which I later replaced with the Firestorm;  another good weapon for ammo conservation) :)  and a melee weapon, first a combat knife, later a machete, then a katana, then Soulstealer.
The necrotic armour from Infernal Lock was a fortunate find, since up 'til that point, every suit of armour I wore got battered and destroyed, since I took full advantage of the build's benefits of low hp, so it was nice to finally have something that was self-repairing.  :)  (I worried a bit about the necrotic armour draining my hp at a bad time, taking me below the Survivor health gate and getting me killed, but fortunately, it didn't seem to drain my hp fast enough for that to be an issue)
That "Blind Luck Medal" came from the one instance in the whole game that I really used the Survivor's health gate feature.  I got zapped by an archmedusa, because I mistakenly thought it hadn't charged up a shot, and I fired a Firestorm shot at it in a situation where I had no cover, and it would have been wiser to run away.  (Oops!)  :o
I also made a recording of myself playing the last level.  I would have preferred recording the whole thing, and normally I wouldn't bother posting a single level, but Sylph made a comment about how she'd like to see more videos from me, and I thought, "aw, what the heck?"  :P  Anyway, 
here it is!  :)Tormuse, level 18 Marine,
defeated the Harbinger against all odds.
He survived for 13257 turns.
The run time was 8h 18m 55s.
World seed was 3775.
He scored 11912 points.
He witnessed the APOCALYPSE!
He was an Angel of Light Travel!
CALLISTO L2 - Volatile Storage
CALLISTO L5 - Secure Vault
CALLISTO L5 -> Callisto Docking Bay
Europa Concourse - Lockdown
EUROPA L5 -> Refueling Base
Refueling Base - found Firestorm
IO L2 - Volatile Storage
IO L5 -> Infernal Lock
Infernal Lock - Cleared!
The Shattered Abyss - found Soulstealer
The Shattered Abyss - Cleared!
Dante Inferno - found BFT 10K
Dante Station L3 - The Hunt
Awards
  Explorer Ribbon (+100)
   * Visited all encountered special levels
  Blind Luck Star (+50)
   * Won despite getting down to 1hp at some point
He killed 1015 out of 1256 enemies.
 46 former grunts           12 security sentries
 1  former CRI grunt        8  military sentries
 12 former grenadiers       26 CalSec bots
 5  corrupted grenadiers    13 security bots
 4  former CRI  grenadiers  4  guardian bots
 13 former soldiers         55 reavers
 27 corrupted soldiers      46 cryoreavers
 9  former CRI soldiers     30 toxic reavers
 2  CRI soldiers            59 archreavers
 6  former sergeants        10 kerberi
 5  corrupted sergeants     7  cyberi
 3  former CRI sergeants    12 cryoberi
 20 former guards           3  toxiberi
 2  corrupted guards        7  medusae
 6  former commandoes       20 archmedusae
 12 corrupted commandoes    27 ravagers
 2  former CRI commandoes   19 armored ravagers
 2  CRI commandoes          6  siege ravagers
 2  former heavies          20 plasma ravagers
 2  corrupted heavies       31 CRI marines
 8  security drones         5  CRI bots
 46 fiends                  14 guardians
 8  fire fiends             3  sentinels
 19 ice fiends              8  warlocks
 31 CalSec sentries         3  archwarlocks
Traits
  Furious L2
  Hellrunner L3
  Tough as Nails L3
  Rip and tear L1
  Cover Master L2
  Angry Motherfucker L3
  SURVIVOR L3
Trait order
  Hr->AMf->AMf->AMf->TaN->MSV->Cov->Cov->
  RaT->Hr->MSV->TaN->MSV->Hr->TaN->Fur->
  Fur
Equipment
  Slot #1 : AV1 7.62 sniper rifle +BC
   * Freezing 2
   * Auto-calibrated
   * Speed-loader
   * Hunter 6
   * Scope
  Slot #2 : Firestorm
  Slot #3 : Soulstealer
  Body : necrotic armor
   * Necrotic
  Head :  - NONE - 
  Utility : AV3 auto AMP
   * Automatic reloader
   * Auto crit system
  Relic :  - NONE - 
Permanents
  Medusa's Curse
  CRI backpack
Inventory
  7.62 ammo (x100)
  7.62 ammo (x100)
  7.62 ammo (x16)
  military stimpack