So, I ran a 2 hour 15 minute speedrun to beat Bard’s Tale 1 with one hero in the party and without any deaths, inclusive of time spent rolling. I started with a H-Elf Conjurer and leveled him up to a 13 Conjurer, then 13 Magician, then 13 Sorcerer, then 37 Wizard.
I used a level 1 Hobbit Bard to hold only the crystal sword so that the Crystal Golem in Kylearan 1 could be passed and the Onyx key obtained. The Bard accompanied me into Mangar (everyone needs a sidekick) and accidentally obtained the Silver Circle, which he promptly dropped and the Circle was re-obtained properly by the Wizard.
He died to traps before he participated in the last two fights (Red Dragons and Mangar), but I figured his next of kin deserved that 300k xp and gold for his noble efforts in holding a crystal sword in the face of a horrible monster far beyond his powers.
The Possession Trap was gratefully a breeze. And the Mangar fight with Thor + Wizard went very well. Started with DMST on the Demon Lords, then DEST on Mangar, then REDE or DEST to get rid of the remaining nasties. The fight went really well, Kylearan came, and the game was over.
At level 37, the Wizard repels all spells and can only be killed by critical hits or stone touches, or thrown into chaos with possession/insanity attacks. So long as the Demon Lords die quickly, the final fight seems more or less easy.
I think that the game can be beaten solo faster than it can be beaten with a party of 4. With some strategy changes, I think 1 hour 30 minutes would be a relatively easy mark to obtain. Using a level 37 Wizard was overkill, and there is very large amount of room for efficiency increases.