You're definitely gonna want to get an IAS skill and a bow with a short(er) refire, because you're correct; CG only interrupts on arrow hit, there is no lingering effect (

). I personally use flurry+shortbow.
Apply Poison isn't really necessary. The idea behind using Practiced Stance and Choking Gas is to keep CG up constantly, so that there's never any downtime to use apply poison. Against non-casters, you're kinda out of luck, but CG does give a benefit of more damage, just don't use flurry (if you're even using it) to give you that nice bonus. If you claim it's an anti-caster build, you shouldn't have any real focus against non-caster (a decent team should be able to pick up the slack)
You also have no way to stop the caster from simply running away from you (if you're using a shortbow, they can beat you easily). I personally use Pin Down as an opener, then lay down the CG hurt.
You should also try to fit debilitating shot in there somewhere. Think about it. If you hit with debilitating shot while using CG, you interrupt (they lose the amt of energy used in starting to cast), AND they lose 10 energy. For more expensive spells, you're looking at 35 energy gone.
Other things you might want to try:
Called Shot/Favorable Winds/Recurve for faster flight time
Nature's Renewal, if your team's build allows for it
Hunter's Shot instead of Penetrating Attack (5 energy vs. 10 energy; more spammable)
Conjure X + Elemental String if you really hunger for the damage. Could get nasty.
CG builds are a lot of fun, but require a lot of patience and a lot of concentration. It's not a sleepy way to play. You have to constantly see what caster is being a PITA and take them out. Depending on what skills you can pack, you can be an asset to the team (warrior adrenal skills compliment bow IAS very well; hang with your own casters and snipe, drop shouts for your team, etc.)
I got some good suggestions in
my CG thread a while back. You might find some nice things there.
Good luck!