If you can beat every single boss without taking damage, you can definitely beat midir. You just need to learn his moveset, not lock on if you're standing close (most deaths are because of this exact reason), and make sure not to get hit by the laser as it's an instant-kill for most players.
Could be you have low vigor though. Every mistake is instantly punished if that's the case.
It's definitely NOT badly designed, no matter what the salty parry scrubs say. His moveset can be avoided rather easily. I beat him last time with 12 flasks remaining, and I'm no expert.
Just be patient, only attack his head unless you can get a free hit in against his legs when he passes you by. Roll through his fire if it comes from the side. In his first stage, the laser can avoided completely by siderolling, then, once he raises his head to do a side swipe with the laser, just sprint forward. He will miss and you will get a free hit or two for his head.
If he points his head to the ground for a fire breath, run BACKWARDS, not towards his tail. If he does his charge attack combo, just dodge THROUGH it.
If he flies overhead and breaths fire in a straight line to the side, sprint to your left side, his fire will miss completely. You can get a safe hit or two in when he lands.
Every other melee attack should be dodged regularly, but not while locking on to his head. If he stands up after a melee combo, run AWAY from him. His fire breath should miss, and as he raises his head, you can sprint towards him and hit his head.
If you end up behind him and close to his tail, he will swerve and strike you with a tail swipe. Roll through it.
Just ignore his dark power up AOE attack. Roll backwards or just casually run away, then as he roars and misses the attack, get to his head again and attack once or twice.
If he summons humanities, run away from his head, then as the humanities move towards you, either dodge a couple of times, again AWAY from midir, or just sprint away. The humanities will miss 99% of the time. Be careful, as midir will start attacking while the humanities are crashing in the ground. Don't get distracted by them and focus on Midir's attack instead. It's likely he will do a melee slam attack, which can be easily avoided, but be cautious nonetheless for his more spammy combo moves.
As for his second stage death laser. I have no tips other than to try and predict where his laser will go by looking at his head. A forward line laser should always be avoided by rolling to the side, away from the laser. A side swipe laser has the highest chance of hitting as it's hard to predict just how close the laser is to your position, but he will definitely raise his laser if he misses anyway after the first attempt, likely letting the second laser get behind you, running forward is a good choice in strategy at this point. Keep attention to him and don't attempt to attack, as the laser combo keeps going for quite a while and every hit is an almost guaranteed instant kill. Naturally, always remember that explosions follow every single laser trail.
And that's basically it, my man. A lot of the difficulty in the fight is due to players panic rolling or locking on to him. The dodge windows for his melee attacks are very generous, and you can dodge through the fire from the side, so you don't need extremely fast reflexes like in the Pontiff Sulyvahnn fight. I can guarantee that if you can handle the pontiff's ridiculous spammy bull**** of zero telegraphing without getting hit once, Midir is a cakewalk in comparison.