THIS IS HOW I CLEARED DARK DECIMATION WITH 4 STAR GEAR 12 CHARACTERS

I cleared the event with all characters at 4 Star, Gear 12 and only minor ability upgrades.

The only abilities I upgraded were Maxing Fractured Fury and maxing Maul unique Always Remember, I Am Fear.

I upgraded the unique because it marks the strongest Unaligned Force User, essentially turning him into a tank during the fight. I maxed Fractured Fury because Maul is the main damage engine throughout the battle.

No other investments were made other than the ones listed.

MODS (VERY IMPORTANT)

Maul: 6 piece Speed set with my best speed mods. His speed is the single most important factor that made this clearable.

Vader: 4 Offense and 2 Health set. Having a strong damage and health mix on Vader was the second most important part.

All other characters: I just auto assigned some leftover mods. Nothing optimized.

STRATEGY

Wave 1
Focus down Luke immediately.

If he opens with his mass assist, consider restarting. There is a chance he will start with only a basic attack instead, which makes the fight much easier.

It is possible to one shot him by using Vader second ability and then Maul second ability, or vice versa. I personally replayed Tier 3 until I managed to one shot Luke at the start, and in my opinion that works best for getting a clean run.

Wave 2
Play it normally and maintain control of the fight.

Wave 3
I personally focused down the Clone Trooper first, though I do not think the target order here makes a huge difference. Just keep control and work through them efficiently.

Final Wave
Focus down enemy Maul first since he is relatively squishy. Once he falls, Savage will fall shortly after, making cleanup straightforward.

MY SETUP

All characters were 4 Star, Gear 12.

No extra upgrades beyond what was given at the end of the era conversion, aside from the key ability upgrades mentioned above.

With some minor RNG, you should be able to clear it at Tier 3 or lower. Good luck.