I was wondering about building a character with this general approach in mind, but thought that Archery might be the better choice over DP. Rain of Arrows can scourge from its own damage ticks, it has slightly higher damage than HoB, half the recharge, a shorter animation, and most importantly can be used from range.
Not sure how that would compare with an AR's FA/Flamethrower combo as I don't have an AR, but FA is a pretty narrow cone so imagine the LAoE of Rain of Arrows would give better coverage and thus more damage?