Hey, here is my version of the Facebreaker Champion utilizing Rallying cry+Pride merc, with added defensive tech that allows to run pretty juiced T16.5 and T17 maps and do deathless ubers on a super-low budget. 7/7 Ubers video:

https://youtu.be/5ViT4SeZpUE?si=OU8GSaxNcXrjPkHn

https://pobb.in/uL7MqtKusRJR  - character

https://pobb.in/kJEnrjLjZxTS - merc gear

I'll break down the main build's ideas:

1. Offensive part is covered by ~1150% unarmed attacks provided by FB gloves+ Runegraft of the bound, paired with 2 slam skills with massive damage multiplier Sunder (625% of base damage with massive coverage) and Earthshatter for bossing (393% of base damage but hits 2.5-3 times), with a huge Merc's Pride aura with ~90% aura effect and Rallying cry providing 25%(before buffs) of merc's weapon damage (1000 phys dmg karui chopper) as a flat phys. I can estimate dmg as:

~25 mill Pinnacle dps for non-crit version (one in the video, a lot of room for possible improvements like awakened gems, 990+ FB gloves, double corrupts etc., at least 20% more dmg could be achieved)

80+ mill Pinnacle for crit version, giant ceiling for sure (pobbed 150 mill with Bottled faith, clusters, massive threads of hope etc.)

2. Defensive part is based on Glorious vanity (Xibaqua) + Fourth vow interaction (50% of elemental damage taken as chaos and then mitigated by armour), on a 30k armor character with Saffel's frame (+4 to ALL maximum resistances including chaos) we in fact reduce elemental damage taken from hits by 50%(Excluing some really huge ele hits like Atziri's flameblast). After that, it's reduced even further with 26 stacks of non-conditional fortification and 7 endurance charges. The main issue is damage over time encounters like ignite, phys and cold dots, so we have a ~1300 life regen and 10% less damage taken over time mastery to give us enough time to run out of degen zones. 

Max resistances (~85 all) are provided by the shield and x4 +2 max res jewellss, if you want to feel excellent on Ubers you should have a swapable different max res jewells to get 90% res for a respected encounter.

3.  Quality of life

To have a good time on mapping, you must use the adrenaline swap tech every ~26 sec (20 sec base with a runegraft of the warp 0.7 duration multi), 2 manual warcries every 5 slams or 1 cry every 5 sec to keep up the onslaught.

Adrenaline swap tech - Corrupting Fever + lifetap + second wind on the weapon swap (X button), 1 press of CF should take just enough life to proc adrenaline (don't overlvl it)

4. Merc requirements - lvl83(84 from T17) Swiftblade with pride, rallying cry + duration and cd supports ideally

5. Regex for T17 - skip drowning orbs, sawblades, exarch pedals, flask meteors, - %max res, more than 1 extra ele mod or pen mod (you can run pen modes with Xibaqua), and - 3% action speed mode. Crit is doable if you can double corrupt shield or body and take the 30% mastery. No leech and 60% less recovery is doable due to "15% warcry recovery" mastery.

6. Budget on trade league. Take into consideration that the build was assembled on SSF with like ~80 hours of playtime. You can probably buy all the uniques for a couple of divs, some basic life+res gear and 800+ phys dmg merc weapon for the rest 3-4 divs. You don't need to have perfectly rolled t1 rares or exactly the same cluster jewels. 

Short gameplay loop explanation:

You enter the map, use 3 manual warcries to get rage, charges and onslaught, you swap weapon to use Corrupting fever adrenaline tech and you good to go. You can use 1 manual warcry while mapping (Rallying cry) and use second one for tought rares. On Pinnacle+ bosses you swap for Earthshatter and use a warcry after each slam, your merc uses rallying cry with close to 100% uptime.