Currently playing as Salvador at level 65 on PC and was very disappointed with the Haderax fight in the Fight for Sanctuary DLC. The arena though was brilliant. As soon as I had paid the 20 eridium I climbed on to the lower ledge, stood at the back behind the rocks and took absolutely no damage to shields or health in well over 30 mins of battle. My weapons were a level 65 DPUH, Grog Nozzle, level 65 Incendiary Lyuda and level 64 Slag Dandy Snider Sniper. Other weapons included a level 65 Homing Slag Transfusion grenade (0.5 fuse) and a Chaotic Evil Monk Class Mod. Progress was slow but just before I reached the half way point on Haderax’e life, he starts a run to recharge his health. Before I could switch to the slag sniper and release a couple of grenades to prevent the regeneration process he was back to full health. This cycle continued several more times. Playing as Salvador I could regenerate ammo, so it must be sole destroying for other characters. I had read that a good weapon to use was a Conference Call. Using a level 64 CC for a while I found that it scored absolute minimum to no damage what-so-ever. After about 35 mins I just stopped playing by using Save/Quit Continue. Haderax is the most frustrating Boss as it seems that “ordinary” players would never get the chance to defeat him. Are there any tips that may make the fight a bit more rewarding?
I’m no raid boss guy but that’s kind of Haderax’s thing, he regens health so must be burst down… They key is the crit spot on the back of his head… You need to tag that enough times to stagger him which causes him to fall over and open his mouth… Then you have to burst him down the rest of the way after… The point of the CC is that the pellet split can hit his crit spot without having to jump up on the rocks… You can prevent his health regen by slagging him in that phase… I’ll let the actual, good raid boss guys like @nat_zero_six , @Slif_One and @Brantron give more details… The latter guy is a Sal main too
This is the deal with raid bosses in general, they’re supposed to be fought by a party using endgame gear/builds. That’s not to say that they can’t be beaten solo.
Haderax in particular can be the hardest or easiest raid boss depending on your approach. As Chemical said, the difficult to hit crit spot on the back of his head is the key, and the Conference Call makes this trivial. Factoring that out, the “hygiene” set is designed specifically for this fight. The Toothpick and Retainer both drop from the sandworms in the area before Hade’s arena (forgot what it’s called lol)
If you have a CC, positioning is key, getting underneath Hade when he emerges so you can fire upwards at him is what you want to try to do so the splitting pellets will hir his crit. When he drops below 1/4 health, he enters his regen phase. During this phase, you need to deal damage to him before he dives underground or he’ll regenerate. If you don’t know the pattern, you’ll miss most of the time, and spores will spawn to disrupt you. This is the most difficult phase.
Raid bosses typically require specific gear to beat, and Hade requires a very specific setup, as well as strategy and positioning in the arena.
Here’s an example of how to trivialise the fight -
I don’t have any videos using the hygiene set, but I can link one if you want to see what it looks like. The other issue with Hade is that he seems to be very resistant to slag, and you only have a short window to knock him down before he dives underground.
No, I’m on PC
Ok well u can get or gib a CC (fire) and Stand just in front of were he comes up and shoot up behind his head with ladyfist in offhand (easiest method) if u want to not do this and do it the old fashioned way u can shoot him while the boss goes in and out of walls in healing fase with an element if an element is applied the boss will not regen (Average is 3 times then the regen fase will stop)
This is easy method i am talking about above
@Slif_One the hygine set is droped in burrows @knighm if you are to farm this set do vahan’s missions where u put flags up then do the one were he has u and his bandit clan go kill sandworm queens the queens have a really high chance of dropping the hygine set pieces
If you need more help let me know 
i am more than happy too