I'm just curious, apart from perhaps pvp or ranged enemies, or getting trapped in a corner without vault as to why it would be more suitable. I myself prefer caltrops, something about getting a slow effect (with enhanced slow, possible stun, increased damage or crit) makes me think of it as superior to Smoke screen (apart from perhaps choking gas @ L59 and perhaps the bonus move speed).
Though my biggest problem with it, is without caltrops you would likely have to choose Entangling shot for most fights or evasive fire. Because once you get 1-3 seconds away from mobs, what is preventing them from closing the gap on you again without the cool-down up? I myself just think evasive fire won't be optimal for damage and more for people who want to just play lazy.
Then again i'm sure i'm choosing vault for a movement buff can circumvent some of that, but without an AOE slow I think the DH will suffer especially in solo or small groups.