Cantina farming order

No one can say what's best, since we don't know when the next Revan event will be. Anyway, I voted death trooper since he's great in the heroic sith raid, and other game modes as well. But it all depends on whether you want to take the risk of losing out on Revan, the next time he comes around.

When it comes to farming for Revan, it doesn't matter whether you do Mission or T3 first, since you need them both at 7 stars. Outside of that, Mission seems to be a great damage dealer, so I'd farm her before T3. But you need Zaalbar with her.

I’m saying mission.
Better to go for the more expensive, farther from the goal object first. That way it is easier to determine what, if any additional resources (Packs, crystal energy refreshes, Shipments, and Weekly Store purchases) you will need to invest to cross the goal line. But since one doesn’t do you much good with out the other (and since you don’t already have a Chex mix team, I am assuming your guild is still in the preparatory stages for the Sith Triumvirate Raid), I would advise farming Mission to 5 Star as well for now, then keeping their shard count roughly equal as you build them up. Since the energy for their nodes comes from the same source, and you need them both finished at the same time, this allows you to ‘double-dip’ on having opportunities to get shards for both of them from the above mentioned sources if it comes back around too soon and drops you into ‘panic farm’ mode.

(Full disclosure, I did not heed my own advice here and farmed T3 to completion first - because droids are a pet project of mine, and I was banking on the rumored General Grievous re-work this month to come true, and T3 has an AMAZING droid synergy kit, but without a mitigating factor like that it is almost always better to farm simultaneously from the same source if they are all required to be complete for the event - and yes, I am glaring at Vet Han and Chewie here..)

Now, if your guild is very nearly hSTR ready, you are doing them a disservice by not farming Death Trooper first. Since I can pretty much guarantee that phase 3 will be the largest hurdle in your path, and as the only current source of deathmark in the game, the only higher priority farm than death trooper should be the Cantina only farm characters for unlocking Heroes Journey’s or Legendary Characters - and I only include the ‘legendary’ characters because taking the long-term view it makes more sense to farm a ‘relevant’ character (like Kylo Ren Unmasked for example, as a far superior lead for FO than Captain Phasma in ALL phases of the game, not just for unlocking B.B.-8) as opposed to sinking time, shop currency, and gear into a dated or far inferior kitted character that once used for the event will become very little more than Platoon Fodder during Territory Battles.

That’s my opinion, hope it helps!