First, imperial troopers are the way to go. If you have a decent star rarity for veers, I highly recommend investing in this route. I walked through all 3 tiers with G8 lvl 80 veers (no zeta), G9 lvl 80 snowtrooper, G8 lvl 80 deathtrooper, G9 lvl 80 stormtrooper, and G8 lvl 76 tie fighter pilot (all 7*). I had just average 5* mods, no crazy speed or anything. The only things needed to focus on are: mod snowtrooper for crit chance, and omega all of veers, all of snowtrooper, stormtrooper's basic, and deathtrooper's terminate.
Second, this event gives good rewards (not worth refresh cost, but certainly first time) so, imo, it is worth working towards this set up^. It is relatively easy to farm and has great synergy without requiring crazy gear levels or mods, just omega'd abilities.
Basic strategy: Snowtrooper aoe resets if you get 3+ crits and will generally ohko the "deadly" scouts. If not, next hit from any other toon will do it, thus fueling tm gain machine via veers lead and snowtrooper unique. Save terminate and veers's assist/aoe to apply deathmark/ focus down the beefy elders. Stormtrooper applying expose is very helpful too. I only used TFP because he is fast even though mine is not great. The real crux of it coes from the troopers. I have a 5* g8 shoretrooper, but unless yours is beefier than mine, the first wave of deadly scouts will wipe him out. It is better to let rng spread out those deadly attacks rather than focus one toon. Also oncethe tm machine gets going, you won't need any healer and shoretrooper doesn't provide much offense