First, I assume you mean dungeon/fractal and not open world. Open world is so easy you can do whatever you want although direct damage is more efficient.
For dungeons and fractals, it still depends on what you want to do: solo or group? Those are 2 very different situations. Solo is more defensive and based on staff. For groups, I would say you have basically 2 reasonably efficient condition settings:
1) hybrid build: sword-pistol/focus. Your almost only condition is bleed from sharper image (and duelist’s discipline when the bug will be fixed). The duelist can then apply about 11-12 stacks of bleed, so 3 duelist = 36 stacks. With condition duration and assuming the fight last forever, you can get up to 50 stacks! This is the most efficient condition build if you can keep 3 phantasms up.
2) “real” condi build: scepter-pistol/focus. Now you get more conditions thanks to the scepter but the scepter AA prevents 3 phantasms. Works best if you would not manage to keep 3 phantasms up anyway.
I think it is worth mentioning though that conditions are not as efficient as direct damage in group PvE. But they can be viable if you are not looking for absolute best DPS.
destroys a clone though