Well it's about time i posted this guide, had it written for a long time, but been a bit lazy to polish it and post, still unpolished, but i thought it better to post, then just sit on my hard disk.
Definitely a tough one, and only for people that like a challenge.
Heroic Hellfire Ramparts
Hellfire Ramparts is definitely a challenge in stealthing, it is probably one of the hardest heroic instances I have stealthed through.
I think I spent about 8 hours in this instance over 2 separate occasions stealthing to the final boss, yes I know, 8 hours with no bosses down, I could of done it normally 8 times over, but the game has hit a point where no new content is coming out until Wotlk, so we're always looking for challenges.
The first 3 mobs in the instance should be taken out, the pat on the bridge (Bonechewer Ravener) can see through stealth, so in order to take him out safely we gotta kill the 2 Bonechewer Hungerers guarding the bridge.
Once past the bridge, stealth to the left, stick to the wall and stealth past the barrels, crates and other obstacles, you will see a patrol, 2 dogs and a orc (Shattered Hand Warhound and Bonchewer Ravenger). It's easier if you mark them up, so you can see them through the crates you are stealthing past.
Wait till the patrol is pathing away, then stealth up, you will come to a corner in the wall, wait there until the patrol stealths back past you towards the entrance, a dog may pause here for a while, but he will eventually wander off.
If you stick to the left side, you should easily stealth past the stealth detection dogs that are parked on the right wall.
Continue stealthing up the left side, you will see a wagon of sorts and some crates stacked up. Jump on these to get past the mobs and when your past it stay in the corner until the patrol passes (wait where the chain of the wagon is against the wall), when the patrol passes (heading towards the entrance) you can stealth over to the right wall, behind the fire, watch out for the single orc pat (Bonechewer Ravenger) that has stealth detect, he wanders around and sometimes stops at an anvil for some hammer action.
Stick to the right wall and stealth past the little tent looking structures, you will see a couple of dogs and a orc near a camp fire.
You should be directly behind one of these dogs, and you will see on the far side 2 stealth detection dogs and an orc.
There is space in between these 2 different sets of mobs, that looks like it might possibly be stealthable.
It is! Kind of!
This is where I spent most of my time wiping, each wipe will take about 5+ minutes to get back to this point, so you can see, we had many attempts.
Timing is everything, if you sit and wait you will notice 2 orcs that patrol on their own, it's best to mark these 2 guys up to see them path easily.
You must wait till both of these orcs are in a good position to stealth past, whether they're both on the far right, or if one is on the far right and one has stealthed over to the far left.
For Druids, with your back as close to the wall as possible, unstealth wait 10 seconds and use a soothe animal on the closest dog (near the fire) restealth quickly, and now you should be able to stealth through the gap of 2 groups of dogs, of course being slightly closer to the soothed dog, this may take some practice to gauge the range.
For Rogue, you should be able to do a distract to get past these dogs, of course rogues also have the advantage of vanish as well.
When you get past the dogs, you have to be careful of the stealth detect mobs on the right hand side, I find it much safer to stealth closer to the normal mobs to the left.
(Now for people having an impossible time of getting past this bit, an easier out, is to all gather at the chain of the wagon, wait for all the stealth pats to path away, then take out the 1 orc and dogs on the left and quickly restealth)
Stealth past the boss, and into the entrance of the staircase.
Here you can take out the 2 guards of the staircase, and wait for the boss to path back to fight him in the doorway.
I found stealthing up to the second boss quite easy, but I do know of fellow stealthers that have a bit of trouble with the timing of the stealth detect dog patrol.
Wait until the dog patrol stealths past the entrance to the second boss room, you should easily be able to stealth past the guards and into the room.
You can stealth past the 2 orc casters that are at the end of the hallway, to the far side of the room, be careful not to drop off the edge, that sends you out of the instance.
Stealth back over to the last boss.
Again I've found some of my stealthers have troubles doing this, if they agro the dogs, get them to run up the ramp a small ways as that is a safely rezzable area.
To stealth past them, wait till the patrol dogs walk past the entrance to the 2nd boss, and follow them as they wander up to the 3rd bosses ramp.
Make sure you don't follow too closely and don't walk that close to the dogs on the right.
As the patrol turns left you should be able to slip in between them and the dogs that are stationary on the right.
Set off the event by killing the 2 guards at the bottom of the ramp.
Kill the boss and grab your badges.