Just went in with my old character to test how's Yagluth doing. Used the best armor + serpent stew/lox pie/bread and fire resist mead. Silver sword as weapon (have around 80 sword skill). The wiki claims he has no weakness to spirit damage but when i hit him the shimmering effect from silver sword was there (didn't switch to any other backup weapon). I had no bonemass ability (forgot to put it) and had to heal 2 times with medium potion + 2 stamina pots. The fight took around 5 mins.

Didn't bother to parry, just ran straight to him and just hit hit hit him in melee and when my initial stamina ended took stamina potion right away to continue till out of stamina, then my HP was also quite down and i used the first health potion. This first sequence of attacks already took about 35-40% of his HP.

After that i managed to bait and make him crawl towards me around one of his "finger-stone pillars" a few times (needed to hug the pillar otherwise he used his abilities), this saved me much (awaited) hassle when i needed to wait for HP regen and potion cooldowns.

All in all, soloing him didn't seem much different from when i fought him a couple months ago.