You can replay the event as much as you like after beating it, so I kept playing it after getting Malak to try and work on strategy for my guild.
Light Side was definitely challenging, and I had two main strategies. In both strategies I let him absorb the Jedi on the far right - thus gaining Tenacity Up. This meant that my Mission and Zaalbar could not apply Damage Over Time effects, so they wouldn't gain fear whenever they attacked Malak.
I never let him absorb the two Jedi on the left - but I beat it both with him absorbing the "Crit Immunity" Jedi and not. When I let him absorb the Crit Jedi, I had to get Zaalbar to put 4 Armor Shreds on Malak before he absorbed the Jedi (since you can't crit after, thus no more armor shred).
In both scenarios, you have to get Malak just above 50% health, and then blast him hard. With Crit Immunity you won't have any of your team get Fear, but the hits are lower. Without Crit Immunity, you can land some really big hits, but you get fewer. I found those two scenarios balanced out. The only "RNG" I found after that was whether he Drained Life from Zaalbar or Jolee. Since those two have the highest health pools, they healed Malak the most. Regardless, if the drain keeps Malak below 50%, you should be golden. At that point, just blast away.