TL;DR: Reberta's LB is strong and cheap, building around it can result in high damage.

Most people seems to be disappointed with Reberta, myself included, with all the issues around her upgrade implementation (Death Crimson still broken, Imbue doesn't fit the Crimson Raid > Death Crimson 2x rotation, Crimson Raid doesn't chain properly with BS, Reberta getting outdated DR chains, Ignore DEF bug on her Rain of Spears and Spiral Thrust).

We were so focused on Crimson Death that didn't pay enough attention to her LB:

Destructive Thrust

 24 LS  
 Decrease DEF/SPR (74%) for 3 turns to one enemy   
 Decrease fire, ice, and lightning resistance (104%) for 5 turns to one enemy   
 Physical damage (30x) to one enemy   
 Physical damage (20x) with delay (1 turn) to one enemy   

Her LB is very strong with 30x damage upfront and delayed 20x damage (delayed damage does't benefit from LB damage boost though) and is relatively cheap at 24 LS. The break and imperil's are also applied before the damage, wich makes it also good for Nyx suicide strategies.

So, how would she fares if we ignore her broken Jump and focus on her LB?

I will show this proposed build, made under the same assumptions as Furcula's spreadsheet.

https://ffbeequip.com/builder.html?server=GL#64aa47e0-c76b-11e9-9d66-5b7bd6bc7eb8

It has two Marshal Gloves for the Auto-LB generation, other than that, it is geared for LB damage.

The objective is to use the LB every other turn

This is pretty reasonable with the build proposed.
It has auto-LB gain of 5.5 / turn, wich means 11 LS every 2 turns, so you have to get 13 LS in 2 turns.
Thanks to Reberta's and Zeno's TM LB fill passives, it means 6 LS drops. 6 LS is, specially considering that Reberta's LB chains at two separated points, pretty feasible.

If you manage to do it. You're looking at 8.2 billion damage while chaining with 1 element (wich is about esther's damage) and 9.6 billion (Elena's damage) if chaining with her 3 elements.

Notice that you might be able to pull some back to back LB's due to the randomness of LS drop. Wich can further improve the damage. Having a LB buff such as Rikku's Pouch Eccentrick helps to pull this more often, and with some luck you can even use the LB 3 or 4 turns in a row.

If you manage to get LB going every turn, you're looking at 10.1 billion damage with 1 element (Zeno's damage) and 12.4 billion damage with 3 elements.

Damage Spreadsheet

Auto LB gear

LB Fill Rate Gear

Those who want to play with LB Reberta can add me.
My Id is 437,540,226