I thought I was actually getting good at this game until Arch Tempered Vaal Hazak. Ouch. Solo and grouped, I am a solid 0-fer.
You need to make sure to have miasma resistance 3 and health augment on the weapon, then it's honestly pretty easy. I did wipe once on my first try, which is more than AT Kirin, I went with Lance but only guard1 cause I assumed most attacks were light enough but turns out it wasn't the case and I was getting staggered a lot which ruined my mobility so I got hit by a bunch of stuff. I redid the build a bit to get guard 3+(guard 4 I think at first) and it worked out fine, then I switched out of lance for faster kills and went IG. Did a kill on cluster HBG too to see if it was as easy as I thought it'd be, and it kinda was, but harder than your traditional monster still since he has a lot of health.
Mostly I geared for miasma 3, health boost 3, health augment on Jho weapons(elderseal for "free" on good raw weapon with some added dragon damage once you break parts), weakness exploit, protective polish, handicraft since I was using Jho weapons(went with 5 on IG build, 3 with lance), temporal mantle+health pod, healing palico. Pretty defensive setup but better safe than sorry kinda of thing.
Make sure to grab those fire bullets things at the camp/around the area and fire at the ground to remove the miasma there and not take additional damage(alternatively can use the miasma expert charm but it's a lot of wasted stats imo it doesn't even hurt that much). I drinked an immunizer on top of the usual stuff too to increase health regen passively. Stick to front paws/abdomen, avoid getting behind him(tail swipe is pretty fast, has a good hitbox and does high damage plus it has followup attacks), if he gets up but doesn't roar, sheath and run away so you don't get hit by the breath attacks on the ground shit(multihits, so can't really dodge it and blocking is pretty meh and requires guard up). And don't go too far or he'll use charges or breath, both of which are annoying.
While you gear defensively, you want to play agressively, so you make use of your health augment to heal up the damage you take constantly from the shitty clouds. Honestly if you're close to him and on the sides, you can just more or less mash keys and he'll miss most shit or only hit you with garbage attacks that do low damage. He staggers a lot too, although he won't trip often.