Yes, Elementalist is great for the Istan farm, especially Palawadan because of the large Area of Effect (AOE) attacks. These attacks easily hit multiple enemies allowing you to 'tag' many of them and gain loot.
Spec: Anything with big AOE's. I like Tempest because it will give you 4 additional overload skills that are also AOE's.
Mastery: Autoloot (Core Tyria Mastery Pact Commander level 5) is highly recommended.
Howto: Just follow commander and blast AOE's around and see the loot coming in. Don't forget to loot the chests.
1) As long as you toss out some AOE's, farming will be a breeze
2) Any spec with big AOE'S
3) Follow commander and the mob of players, turn on auto loot and don't forget your chest! It's easy peasy.
Compared to Thief it is very annoying to me personally, but it definitely works just fine. You'll want to use Staff. I usually camp Fire and switch to Water when my skills are on cooldown, use all water skills, then back to Fire. Your Fire 2 skill will be very useful to tag enemies. If there are multiple champs, like in the Great Hall, try tagging the corner where most of them spawn with Meteor Shower and then move on to the ones spawning elsewhere. You don't need to deal the finishing blow to enemies, so you will have plenty of time to tag the rest before the zerg moves there.
Logging out forever.