Well Gunner, This list looks a might like the Nid lists I've been coming up against recently and I have a few pointers as an opponent.1.
Hive Guard are great... For you, because I as a Tyranid opponent HATE them. To be able to hide behind a building or piece of cover and still pop off S* shots is quite effective, and they're very resilient (except to plasma, but what isn't really?). I like your idea of using them and the Gun-fex as a base of fire as he looks mean too and looks like he's bringing a decent amount of fire to bear.2.
Which leads into my next point. Be careful about stranding them synapse wise, the Prime isn't the toughest (less-so than the Hive Guard but for an extra wound) and will be targeted if possible given the other more tough options in his local swarm. I understand he will be in the squad of Hive Guard but thats why I bring sniper rifles to fight Nids (and to shoot [and get rends on] MCs). And there are other ways to pick him out: blasts, barrages, etc...
You have 3 synapse (Prime, Zoanthropes and Tervigon), which is pretty decent for 1K, but other than your Tervigon, your other Synapse doesn't look too resilient and are basically targets 1, 2 and 3. That's how I'd play it anyhow. Tervigon has to go, Turn 1 if possible, I've seen these guys cause too much harm to just be let to their own devices spawning gaunts and casting Psychic powers. Then it's really a toss up between the zoans and the gunline. I'd probably go zoans cus they're more likely to be sitting NOT with a carnifex.
I'm by no means trying to tell you to augment your list due to this, just to be very aware of what someone (like myself) might try to exploit in a game and make sure it doesn't happen. It's the one BIG chink in the armour that I see. Long point, my apologies.3.
use the stealers to engage their backfield units or exposed flanks.
Ymgarls. Are they going to be hiding in terrain? If so good call, If not, hide them in terrain. This is a day ruiner. I just can't really counter it short of spreading all my units out across all the terrain pieces on the board so they can't deploy, which is just not feasible before turn 2.4.
Don't bet the farm on Regen if it comes to it, I've seen a Tyrant make 3/3 before, I've seen a Tervigon (I know hes not got Regen) fail 5/5 then die the next turn. I'm just saying it's hit and miss.
Let me say finally, that I'm not trying to disuade you here or anything Gunner, I like the look of your list, it looks like it could be punishing, I'm just trying to give you an opponents perspective at how I'd try to attack your list. I'll leave you with a link here to my BatRep Thread. Have a look. I think it could be a great help. Top Down Battle Reports