This build you'll use Echo with Dual Shot, then cast Serpants Quickness. This should give u an almost constant Dual Shot
That's true, but the idea behind a 'spike' is that the dual shot and the following shot land very close to each other which leaves no time to heal or throw up a protect. Dual shot fire's slower than both Punishing shot and quick shot.
But as a single person damage build this might be worth looking into.
only potential problem I see is energy management. Ideally dual shots, with zealous mod, should be almost continuous, but from experience of using 10 energy skills w/ 15 expertise, if I just spam them all the time I do get low on energy on several occasions.