Use your Silver or Black Metal Sword and Facetank him (you survive everything except meteors)
Should take 5-7 minutes, 2-3 Heath Potions, 1-2 Stamina Potions and of course 1x Fire-Resist Potion

Allright I will try that and see how it goes. Thanks !

Gear aside if you have lower skill levels it will make it harder to accomplish

And use the first seconds when he spawns (when the floating points appear) and hit him in this state. So you can deplete about 10-20% of his HP before he is fully spawned.

strongly recommending frostner or the silver sword + a decent shield

I did and he never moved off his alter, so basically good food, fire resist, frostner /padded/black iron round shield and his health felt really low or he is extra vulnerable to the weapon. Just a bit of in and out, run behind a stone to regen stam, block his razorbeam, back in, get hit by meteor use healing potion. Interestingly his ray can be blocked. He is slow enough that you can circle him and get some backstab hits.

Yagluth is much tankier now than he was. I used Frostner and had mistlands-level food and he still took about 15 minutes or so to kill, and that was me standing in the flames wailing on him whenever I got the chance.

I think Yagluth's damage output is fine - the meteors really hurt but are easily avoided, and everything else fire resistance minimizes - but he has a lot of HP/armor and it seems like he attacks constantly.

I should try again and see if I can circle behind him more, that seems to be the way to spend more time attacking than running and hiding from his beam/meteor attacks, lol.

He was stuck up on the altar when I fought him, I spent more stamina repositioning to try and hit him on the uneven ground than I did swinging at him.