Smoke Grenade should be a cloud that lingers for the duration, and the Bonus damage from “Enhanced Smoke Grenade” should apply to all enemies as long as they stay in that area, including bosses.
This might seemingly overlapp with Caltrops, but Caltrops should be something else like: “Enemies are slowed in Caltrops and takes X damage per second. If an enemy is suffering from the knocked down(KD) effect in Caltrops (including KD happening before the Caltrops are applied), it take MASSIVE damage per second.”
Also: a “sub-skill” of Smoke Grenade can go like: “Smoke Grenade now releases a flammable dust cloud. Fire effects immediately consumes the remaining duration and does MASSIVE fire damage.”
(Oh yeah, that means Rogues needs Fire/Explosion Arrows somewhere.)