Well, to be fair, given the context of his question, I think he's looking for some help with a variety of bosses, but only specifically itemized these two, and he was looking for video footage, which I don't have.
That said, I figured I'd give my Hunter techniques some air time regarding the two fights in question.
Pet Survival in Obsidian Sanctum
Pet survival in Obsidian Sanctum with drakes up is pretty brutal. However, even a Survival hunter gets 15-20% of the total DPS from the pet, so we all want to pay attention to it.
I have found some keys to keeping my pet alive when fighting Sartharion:
Run away, little girl! Run away!
Condition the stimulus response.
Stimulus: Ears hear "run away little girl".
Response: Recall pet and locate safe spot in flame wall.
Even with full Avoidance and Resistances, I have found no way for my pets to survive a flame wall hit. Recall pet, find safe spot in wall, watch wall pass, send pet back in, and resume pew pew.
Twilight Torment is a sneaky mechanic. You take damage as you do damage. You need to monitor your pet's health very carefully on this one and keep him by your side if need be during the Torment stage of the encounter.
TT is tough for the Hunter too, so you need to monitor your own health very closely as well. Mend pet, even the dull boring non-talented version that SV hunters have, will help your pet stay in there a bit longer, but be vewy vewy caweful.
This one is tough. With your pet positioned behind a Drake, it can be very tough to spot fissures back there.
It is a shame when you see two or three hunter pets die simultaneously when a fissure comes up in a bad spot.
The flame wall and Twilight Torment are avoidable. The Fissures must be avoided without fail by the Hunter, and do your best to also spot pet fissures.
Hunter Kiting adds on Gluth
This is a fun one. If you're assigned to Zombie Chow kiting duty, you will be playing a role that is entirely different than your job on every other boss in Naxx.
Bye-bye, Pew-pew. Hello, Frost Traps.
In 10-man, this is fun as hell, because you'll likely be the only person doing the job. In 25-man, still fun, but you'll need to coordinate your efforts with other players (other Hunters, and some Mages, in my experience).
The short version of the story is: Drop a frost trap and run circles around the perimeter of the frosty area, shooting at all the Zombie Chows you can see. Drop new traps whenever the cooldown is available.
Step 1- Drop
Step 2 - Blow the Whistle: Recall your pet (since you dismissed prior to entering the tube, yes?) and sic her on the boss. I just leave my pet chewing on Gluth to help out with the DPS efforts. I'm sure that more creative hunters can make use of their pets in kiting, but that's not me.
Step 3 - Pull Aggro: Look for Zombie Chow. They'll generally bolt straight for a healer. You need to nail them with enough damage to generate sufficient threat to keep them off your healers. I find Explosive Shot works nicely. If I have some distance between me and Chows, I'll stand still for a moment to fire an auto-shot for added threat.
Step 4 - Position for Trap Activation: Move your toon such that the Zombie Chow you just aggroed will pass over your un-triggered frost trap.
Step 5 - Round and Round We Go: Run in a circle around the perimeter of the frost trap. The Chow will basically remain stuck sorta in the middle-ish of the trap AoE, continuously turning to follow you, thus keeping himself slowed by the trap. Meantime, you run at full speed, so he never catches you.
Step 6 - Pickup Adds: Keep eyes open for additional Zombie Chows. Here is where it gets a little tricky because you use your mouse for movement to keep yourself running around the outside -BUT- you need to target the new Chows. So I usually briefly use my left hand on the keyboard for movement while I target a new chow via the mouse. It happens very quickly, so there's nearly zero interruption to the movement.
Step 7 - Renew Trap: Ensure frost traps drop as soon as the cooldown's up.
Step 8 - Other CC: Depending on how well the "round and round we go" technique is working for you, you may need to Concussive Shot and/or Wing Clip. A jump shot here or there can be added in for some style points.
Step 9 - Volley: At certain points, all the Zombies will run for Gluth. It'll be pretty noticeable because you'll think you just lost aggro on the entire pack you were kiting. Volley the hell out of them because it'd be bad for them to reach the boss.
There you go. Nine simple steps to kiting Gluth's adds. When done well, Step 5 in Naxx-10 is a sight to behold, as you'll have this nice tight pack of 6 or 8 Zombie Chows just spiraling in the middle of your frost trap.
I'm not claiming to be an expert on any of this stuff, but I do like sharing methods that have proven successful for me.
What other bosses would you like hunter advice on?