Here are my tips to beat him without getting hit even once:
First phase - bait his 1 hit bite or the 2 combo bite and hit once in the head OR go to his front limb and hit once after the 1 bite move after which he'll likely do the dash attack which can be easily avoided by dodging to the back (to be safe dodge twice). When he staggers unless you are in the correct position you'll not visceral him, note that it's hard to position yourself in the correct location so rather do a charge attack instead after which QUICKLY DODGE TO THE BACK as he'll use his body flame attack (or whatever it's called). When he positions himself to vomit lava, you should remove the lock-on and quickly run to his hind limbs and do a charge attack (if you are fast enough you can do 2 fully charged attacks). Rinse and repeat this strategy. Note that he'll sometimes do his hand fire wave and flame bites which can easily be avoided by dodging to the back once or twice (just to be safe do it 2 times or more).
Second phase: This phase is very much the same as the first phase except he'll add come more head swipe to his swipe combo, he'll use his bites more, he has a new flameless diving bite attack (very easy to dodge) and he'll use a supernova explosion. Use the same strategy as above. All of his attacks are to be dodged the same as above. When he's charging his explosion run away from him as it has a large AOE range and you'll be safe. It's also harder to bait his head swipes but sometimes he'll only do one swipe and that is when you should attack his head (or as noted above run to his front leg and attack once or twice and dodge quickly to avoid his charge).
If one is a BT build the 2nd phase becomes much simpler as one can shoot a BMA boosted Evelyn/Repeating at him to chip away at his HP.
If this is done correctly one can beat him without ever getting hit. Getting hit will guarantee one hit kill as elemental attack damage aren't halved in Defiled chalice. It's a fight that tests patience more than anything so the ones who persevere will beat him easily but those who rush will have a hard time.