1-2 Extra Chained Energised Hits and 2.5-10% Impact on Energised Hits.
Increased Cleave and 5-20% Heavy Melee Attack Damage on Energised Attacks.
Critical hit chance scales by your current heat level up to 27.5-50%. Also increases critical ranged attacks damage by 4-10%.
5-8% Strength for every shot fired during continuous fire. Stacks 5 times.
Build I used to get a few hardmode damnation win against the twins in both discord comm and public match (I did not have those perk lock for ps but you can't always get what you want with that crafting system).
While it might still be unrefined, the general ideas worked for my preferred playstyle. I took a wound but I might drop it at some point.
Shredder frags grenade are our most potent grenade for this fight and you cannot get enough of them: while they are less potent than ogryn's frags bomb, you get 3 of them and have a lot of option to keep generating more. While they are not an unlimited resources, we have enough regen option to justify taking grenade tinkerer. if no one use the ammo bo you have access to a great 12 grenades refill, enough to trivialize most elite ambushes. I did not expected much from grenade at first but it turned out to be a really, really good tool.
Survivalist is probably the worst aura for this particular fight, so the choice is between fire team and close and kill. The speed aura felt too costly with a frags build so I went with the damage one.
Voice of command is our best ult for this fight. The ability to reset elite ambush and to top off your team thoughness is invaluable on such a short CD. It also has field improvisation on its path, a talent that definitely found its niche here.
While Focus target is definitely a good pick, a weapon specialist version might also works for a more melee focus version. This would be a very different build though !
The rest is pretty standard as far as plasma build goes. You need to be careful about your reload cycle but I don't think I ever had to reload more than once during the fight Even in hardmode you can find safe window, with both VoC and frags grenade helping for it, as well as animation cancelling. Plasma is useful to reach the few specialist that might appears, to cleave and stagger through elite and to reach the twins from afar with good damage. Your melee game is very important though: do not get in the mindset of "I always need to shoot".
For powersword player I definitely recommend to play sunder with the standard power cycler blessing. This fight throws a tons of meaty melee elite at you, not even counting the boss shield, and the ability to cleave through them means you can stagger way more target than you are expected to. It makes your melee games safer and improves the consistency of Out for blood.
Regarding the boss fight in itself: practice makes perfect. There is already a lot of guide with general advice that I won't go over: you should have all the option you need. If you want a completely different build , I would avoid taking survivalist, exec stance or marskman focus, as well as any low agility gun with bad swap speed. Good luck !