Update as of June 2023:
[Baruuk] is the GOAT for Steel Path Circuit.
Be it Defence, Survival, Exterminate, Excavation or lame Void Flood. He can beat them all up, even Decrees ain't that important to him. Some are, obviously, beneficial, like more damage per owned Decree, or more damage per status effect effecting enemies ([Condition Overload] alternative), but still, you will rock the thing full solo. Unairu is NOT necessary, as I was using it. I had it due to "whatever random combination comes, I can still armor strip them", but I would have rather used Zenurik for energy [Regen] and spamming Lull all over the place, as draining the gauge for a longer Serene Storm duration is a juggle.
No issues with damaging, defending, surviving. Easy peasy!
[Warframe] Baruuk - The Paci-Fisting Brute - The Circuit - Steel Path Lv 680+
The Monk punching your salad is finally real!
You gotta try your best by not being hit? Screw that! You will be immortal! ... well, almost... ! Actually ... yes, you will be immortal.
Steel Path (5minutes)
Without Combo Multiplier:
10k-60k ish Damage Values
With a 11x - 12x Combo Multiplier:
44k-110k+ Damage Values
Here is your build!
Your first ability (Elude) will cover a decent angle with [Stretch] equipped, no need in more!
It is advised using it more like an emergency skill (like Hysteria, Molt, etc.) since it is a channel-ability and continuously draining energy from your pool, which I might add ... a really large energy pool. No jokes. 300 energy is totally enough. (A candidate to be replaced with another ability since Helminth Chrysalis is a thing. Kinda not using it myself for a long time.)
Do always cast your nighty night ability (Lull) as often as you meet following circumstances: New room, new enemy wave, if you have time for it. It has a regular cast delay, but is very effective setting enemies to sleep.
Keep up your daggers (Desolate Hands, third ability) all the time, no matter what. The damage reduction from it will be worth it. Also on a side note, the ability is blocking status effects, when you have at least 1 Dagger hovering around you. Heat/Toxin/Electric/Health Drain (Arbitration for instance)/etc. effects won't damage your health nor your shields, despite the debuff being triggered and visible.
Isn't logged on Wiki nor DE seems to be aware of this (for years).
And those actions, those abilities, you need to cast them to drain your "Restraint"-Meter. The more you drain it, the longer your last ability (Serene Storm) will cause havoc.
I don't know what you might like from the stance style of this exalted mode, but I do recommend the slide-spin attack (alike the Hysteria one) and regular still-standing-wavey style, both will either stagger, lift or even launch enemies. So automatic-CC is quite the thing here.
You can also charge-attack the living shizzl out of your enemies, but the radius is kinda narrow.
Equip your Melee weapon (which will hold your Serene Storm/Desert Wind active), hold block and keep spamming charge attacks. You will stomp the entire time. This is called "ani-cancel" and is mostly known in games like Blade & Soul or Black Desert Online. You are welcome. The damage is high, you might use this power ... for whatever reason!
P.S.: If you wanna pop nullifier bubbles without using a [Miter] with the respective mod of doing that instead, just jump and downward attack (not as a charge attack!) near the bubble and you will most certainly pop it in one bash.
You can easily butter through enemies Lv 300+, tested [Baruuk] with this build at Arbitration, Steel Path.
Definitely the most potent frame.
Sure, [Khora] can dish out tons of damage too, but her survivability is just literally non existent without her constantly upkeeping her Dome around and camping near it.
The damage reduction of [Baruuk]'s 3rd and 4th + Adaption is incredible!
We won't need any kind of Duration. Your Lull ability needs to be the shortest possible, so you can more often use it on the same enemy to drain your restraint meter even further. It is more effective on hordes of enemies than using Elude and wait their stupid AI to trigger a simultaneous attacking pattern (which never happens too often).
[Primed Sure Footed] seemed to be the best deal on this frame, as you will have moments inevitable that enemies will get too close, where you also need to get closer to them. Each dagger drains a good amount of restraint, so unarm the enemy whenever possible to get a good chance of never running empty on Serene Storm!
As for the Arcanes, go with Arcane [Fury] and Arcane Augment. You will love the damage output (check the Desert Wind Build more below)!
Magus Elevate is always a must-have for your Tenno-side Arcane setup. Try to get them to Tier 3 or 5. Since Elevate does trigger at its own instance, unlikely most of the other Arcanes (for instance, you cannot trigger twice Arcane Guardian/Grace/Aegis/etc. anymore), you will have the potential healing enough health with each Operator cast.
We will use Zenurik OR NARAMON (more down below) with this build. Why?
Naramon is a waste of time. Only direct physical hits with your FISTS is adding up to the combo counter. Not the waves!
Vazarin and Madurai are not necessary. You are tanky af and your damage is already over the top. Most of the players will never see its limits.
Just dash sometimes with Zenurik to replenish your energy pool. It is just for Desolated Hands, when running out of daggers, and Lulling enemies from time to time.
Naramon. Why use it now? As I was not aware of this fact, I knew that the waves do not generate combo, yet they do profit from the multiplier (not on an external stat-stick, which most of the Tube-Morons suggesting and lying about).
The damage output is quite higher, more than double, when maintaining a high combo multiplier, for some reason. We are not able to use any Acolyte mods ([Blood Rush], [Weeping Wounds], etc.) and the damage output can be seen in the videos and screenshots above. So, something gets differently calculated for whatever reason. Typical DE logic.
In this case, I would actually suggest using Naramon instead of Zenurik, IF you are owning a [Dethcube] with [Energy Generator] and a good Sentinel weapon (Verglasfor instance), since you have to recast your second and third ability as needed.
Let the enemy simply engage you while your Serene Storm automatically blocking every incoming projectile/melee hit and thus increasing your combo meter.
Why no Stat-Stick?
Because people are braindead talking about physical weapons do help with [Baruuk]'s Serene Storm. [Baruuk] is the only frame which does NOT profit from external Melee and Riven Mods on your actual Melee. He has not and has never. Don't let people on the market with Riven-Arguments and Youtubers with no brainer content like Grind Squad fool you.
Only the typical Gladiator mods are working, but also not necessary due to already extreme high damage numbers, since Orange and Red Crit Numbers ain't the thing. Even a low end weapon can red crit (tier 3 or 4) but can do jackshit against high level enemies.
[Desert Wind] is currently one of the best augmentable abilities out there. [Reactive Storm] will adapt to the enemy's vulnerability (e.g. Corrosive against Gunners, Radiation against Bombards, Fire against Chargers, Magnetic against Shields, and so on).
On top of it, you will punch the crap out of everything in your field of view, since the waves launching from your ability are punching through infinite enemies. Only walls and such need to be experienced. There are some meshes/objects which can be penetrated, others not. Same goes for Floors and Doors.
The Build: Serene Storm (does apply to the primed as well as to the normal one, doesn't matter)
Additionally, try to use Primary + Secondary Dexterity, as the combo duration (15s in total) bonus do apply to Desert Wind / Serene Storm. This will render Naramon unnecessary and you can go with every focus school you want instead.
Last but not least, don't forget to cast Empower (50% flat Power Strenght buff) to increase the impact on Desolate Hands (more daggers) and Serene Storm (more damage).
Best regards and happy hunting, Tenno!