I managed to pull my 4th bonus unit, so I tried using Exdeath and friend Randi to carry me thru ELT. So far, consistently clearing, no losses!

F2P Exdeath - 519 MAG with Ramuh 2*. Wizard Rod Stellar Shield Creepy Mask Force Armor 2 Earrings, 3 MAG 10% and Equip Hat.

4 Bonus Units: I am lucky to have pulled Randi, 2 Primms and Popoi. No need for elemental weapons (yep, no chaining needed here.), BUT you MUST have someone who can Faith (Shiva), Imperil (Diabolos), and Deshell (Carbuncle or Siren). If you have your own Randi, he is on Full Moon Slash duty (replacing the need to deshell). You may not need your own Randi (any Primms and Popoi will do) as long as you use a...

Friend Randi - preferably with DW so he can use Full Moon Slash and Slice Thrice twice. So Slice Six? Nevermind. 500 ATK will be perfect.

Here's the plan:

Round 1 - Faith on Exdeath, Deshell or FMS, Imperil --> DC Blizzaga. Friend Randi can just wait or auto attack to save MP.

Round 2 - Hopefully RABITES! If a huge weirdo chicken appears, press repeat. Regardless of the sequence of the repeated abilities, chickie will go down.

Round 3 - Press repeat! Promise! In case he doesn't go down, friend Randi uses Slice Thrice.

Round 4 - Press repeat. Yes, promise.

Round 5 - Press repeat. Not kidding.

Round 6 - Press repeat. Likely won't OTKO, but he won't be able to kill off your team. I usually follow up with DC: Blizzaga Osmose to top off some mana (not usually needed.)

Round 7 - Faith on Exdeath, Deshell or FMS, Imperil --> Wicked Light Slice Thrice. May not OTKO, but you'll survive to wipe the next turn.

Hope this helps someone with a similar predicament (no DFina, Noctis) who wants to grind out candies.