LF fun farming build with flamethrower
Slot mortar elite (now a kit with 1500 range autoattack) for long-range tagging since they nerfed grenade range, otherwise run any AoE option you fancy.
Grenades are still best (and currently bugged to hit twice), FT/bombs have problems getting into range if mobs approach from multiple directions, can be instagibbed at their spawn or at certain world bosses (golem, behemoth, fire ele)
Trait selection should be pretty straightforward, AoE damage procs and +%dmg wherever possible. Make sure you have either Mecha Legs (Inventions) or Streamlined Kits (Tools) for open world movespeed.
You might consider Sinister stats instead of zerker, especially for nades/FT, but getting those requires a lot of Silverwastes farming. Condi still sucks if mobs die too quickly, such as Ulgoth pre or Orr mobfarms.