If the first response of the dragon is to just run, then the hunters either need to be able to kill/incapacitate the dragon very quickly, or have some way of immobilising it.
Immobilising a large, strong, flying creature is not going to be easy; the hunters will need to be very well prepared. The first thing they will need is knowledge - not just of dragons in general, but of the specific dragon they're hunting. The first group of hunters will be scouts - specialists in camouflage, tracking, observation, and information-gathering from locals.
The second specialisation of hunters will be a commander - someone with inference/deduction skills and knowledge of dragonkind who is smart enough to, based on the scouts' observations, be able to find patterns in the dragon's behaviour and the locations it visits and make a plan.
If the scouts' information is incomplete, preliminary skirmishes might be required to test how the dragon reacts in combat. These skirmishers will be trained in the use of bows, lances and quick disengagement, mostly attacking in packs and scattering (so in the worst case, only one dies) at the first sign of aggression. They do not use highly effective weapons, and have several layers of woollen blankets, etc., that they can discard if covered in acid and are dull brown-and-grey coloured so they can attempt to hide if needed.
The final attack will take place either at one of the dragon's lairs, if it can be found and is suitable, or at a tempting location - details will be specific to each dragon, but the scouts should have uncovered something. The strike force will include:
- Net throwers, with weighted, barbed chain link nets. They will be inside the range of the dragon's spit, so this is one of the most dangerous positions, and multiple will be needed, because a single human can't lift or throw a net big enough to restrain a dragon like this. These hunters don't do anything else, they just train to throw big nets as far as they can, although they will participate in stabbing once the dragon is incapacitated. The barbs on the nets won't hurt the dragon but will get caught in the scales. Some large nets may be mounted on siege equipment, but that will have limited ability to target accurately and to conceal effectively from the dragon.
- Tanks, who may be same as the skirmishers from test battles, since their equipment and skill set is similar - covered in dragon-resistant armour, padding, and blankets, and acting solely as decoys and to get net throwers out of danger. They will also have short staffs - metal poles about 5 feet tall and with spiky knobs on both ends. These are for holding upright if you're quick enough to realise the dragon is going to bite you - it bites the staff instead, which will hurt it but more importantly stop its jaws from closing on you. Tanks are also the ones who decide who to save; they're good at guessing the extend of wounds and viability of the wounded hunter, and know the more valuable hunters (e.g. lassoers) need to be saved first.
- Heavy crossbow, who shoot from hiding, preferably from above. They will target legs, wings and shoulders first, trying to slow down the dragon and prevent it from escaping or killing (too many of) the hunters. The head will be too difficult a target at first, so focusing on the dragon's mobility and claw/wing attacks is the first priority. Not much they can do about the tail.
- Ballista, hidden at first and uncovered once the dragon is in the right spot and at least partially immobilised. The dragon will obviously target it once it knows about it, so they usually only bother loading one bolt in it - it either works or it doesn't.
- Lassoers. A complement to the net throwers, these focus less on reducing mobility and more on removing the dragon's methods of attack, especially the head and tail. They lasso a part of the dragon and then tie the rope to a pre-prepared stake; they are also able to use the stakes as a sort of pulley to pull whatever bit of the dragon they lassoed further down (friction prevents the dragon getting further away, and every time the dragon gets closer the slack is taken up again). The main job of the lassoers is to take out the head and tail; if they can lasso the head but can't pin it (because the dragon is still too mobile), they will attempt to at least draw the noose tight enough to restrict the dragon's neck and reduce its ability to spit. Particularly skilled lassoers can try to lasso two parts of the dragon to each other, which will very effectively reduce its movement and ability to fight. They're in range of the dragon's spit though, so they're vulnerable; they will hide behind a tank as much as they can.
Most hunters won't wear much in the way of armour, since it's not much use - a dragon bite can be expected to crush even someone in plate armour. Basic leather protection would be useful against glancing blows, with padding (helmets are a must, too) since they can expect to be thrown around a lot. Mobility will be more important than armour. Face shields won't save a hunter from acid, but they might soften the impact - useless if you get caught in the middle of a stream of acid, but good to protect against smaller splashes.
The opening shots will be from a siege net thrower, if available; after that the tanks will charge first, so the dragon is more likely to target them, shortly after which the others will do a coordinated attack while the tanks run around. If the dragon is able to be immobilised/dragged into the ballista's range, it will be used; if it can't be used or doesn't kill the dragon, once the heavy crossbows have weakened it enough and the dragon's primary attacks are not a threat, everyone can jump in with whatever stabby implement they have.
If a dragon cannot be weakened or immobilised enough, the hunters will need to abort. Their survivability will be low against a dragon they've managed to piss off, but it will be better than staying in the fight without the resources to finish it. They will attempt to scatter so at least some will survive - those hidden (such as the heavy crossbows) will just stay hidden, the rest will just run and hope for the best, accepting that the dragon will catch and kill two or three.
In some situations the hunters may be able to use more elaborate traps, such as oversized bear traps, large nooses, falling rocks/rubble, and pit traps. These require yet more specialised skills to create effectively and won't be able to be used in every fight (heavily location-dependent), so not all teams of hunters may have them.
A very effective technique is to snare the head of a dragon (either with nooses/lassoes or with falling rocks) as it looks into a hole only big enough for its head, but it is too dependent on a good location and a stupid dragon to be something the hunters can use often.
There will be a recovery and care plan for wounded hunters so they can get out of the fight and be patched up for the next one, considering how valuable their individual skills are. Hunters unable to fight anymore become trainers; particularly experienced ones may become commanders.
Considering that even on a successful hunt the dragon hunters will usually have casualties, many of them fatal, they would not embark on hunts unless they have enough members in reserve to cover losses. They'd likely be organised into teams, with a team consisting of twice the members needed for a full hunt, plus their own commander and trainers. They'd have relatively stable memberships since a close rapport is needed to effectively carry out a hunt, and they wouldn't interact much with other teams other than occasional sharing of members and rivalries. They would occasionally recruit their own members, but would rely heavily on the organisation to fill gaps left by death and disfigurement.