You shouldn't particularly fixate on poor DPS from your SV hunter. That being said, they can easily do comparable DPS if played correctly.
Ayukawa should have 800 or more unbuffed agility, and it's entirely doable in worse gear. As the poster above me said, they need to change out
[Ring of a Thousand Marks] for something with Agility on it. Their meta gem is another issue, it should always be
[Relentless Earthstorm Diamond] for raiding. I hope the only reason he/she has AP gems in their BP is because they're dirt cheap on your server. They're more expensive than the 8 Agi on mine. The two gems in the belt
need to be changed to something with Agility on them. Another "easy" fix is that I know a lot of SV hunters like to use
[Belt of Deep Shadow] over Ayukawa's current belt.
Sieta looks pretty solid in terms of gear, but I'd recommend getting
[Hourglass of the Unraveller] or
[Abacus of Violent Odds] instead of his Skyguard trinket,unless he's using it for farming. Given the nature of PvE encounters, especially bosses, the proc won't happen enough to be worth giving up the benefit of another trinket. His hit is also a little low, and it does like he had at least a couple misses on WWS. It should be at least 136 or more for MM and BM hunters. His DPS could be upped even more by using Arcane more often. If he's worried about mana, tell him to make sure he's using
[Fel Mana Potion], it's like hunter crack.
For Chaoticid, obviously enchant those nice fist weapons then lemme link the Armory to my rogues to make them mad...kidding, of course. Again, the hit is a
tiny bit too low. Hunters can completely illiminate misses with the proper hit rating, which is why every raiding hunter should harp on it. IMO, Ebon Netherscale Bracers are better than True-Aim. As opposed to Sieta, his RAP is very low. I would also change out
[Romulo's Poison Vial] for Abacus or Bloodlust Broach. If you look at WWS and have he/she look at it too, you'll see that that trinket isn't really doing much at all. Also, using Arcane shot more would increase the DPS.
The Steady/Kill Command macro is great, but you shouldn't be using it and nothing else.
Again, with Lawnchair, he should change some gems, dropping AP for Agi. Otherwise, what he's doing with the gear he has looks pretty good. However, he would probably benefit from using AP flasks instead of the current consumables he has. I do see the Fel Mana potion debuff up so he's doing something right there also. Using Multi is fine, but he should be using Arcane more.
For Yealix, again on gems, Agi > AP. Helm should have an 8 Crit, and while I'm addicted to the 8 AP/2 mp5 gems, you
will get more out of 4 Agi/6 Stam. He/she should also be using the Ebon Netherscale Bracers, to up their crit. Their hit is also painfully low. And again, they should be using more Arcane shots.
In terms of something across all your hunters, a good rule of thumb that I like to follow is that you ignore
all socket bonuses
except those that add Agility or Crit, putting 8 Agility in everything else. Under most circumstances, this should get you your meta bonus with sacrificing the least amount of Agi or ranged crit. For the most part, in terms of gems and enchants, Agility is always better than Attack Power because it will scale with Blessing of Kings.
Overall, I think your hunters are doing at least decently, but you should really change up your raid composition. We always have 2-3 rogues and unless it's Karathress or a melee-unfriendly fight, they're on top by a good deal. Do you normally have any Spriests, DPS shammies, or ferals? Your raid would probably benefit from that. However, if what you're doing is working for you, then why change things?
Okay, to wrap it up:
Your hunters should all be going for Agility over AP on gems and enchants. Agility scales with Kings whereas AP will remain a flat stat. For example, I only have ~2300 RAP unbuffed as MM. I was using all AP gems, and came out at 2700 RAP. I'm at 2947 raid-buffed with the Agi changes.
All of your BM hunters need to be using Arcane shot everytime the CD is up. Only one of them is above the hit cap, which is a big bad no-no. Besides your SV, they should also use
[Flask of Relentless Assault] because they're benefit from it more than they will a combination of elixirs, IMO. You might also want to try out having an MM, granted our utility is terrible in terms of TSA. However, having a hunter or two with Scatter will feel pretty invaluable when you're doing Kael trash.
Hunters seem to be the main source of DPS in your raid so make sure you're grouping them appropriately. Have your SV in a group with 2 BM (1 MM, 1 SV, 1 BM ideally, but since you have no MM) along with an spriest and either a feral druid, enchance shammy, or second spriest. Make sure you're using the rest of the BMs to buff other DPS classes as well.
Sorry for the length, and I hope I helped at least a little bit.