Although I stayed with the Sniper, using your suggestion, after several unsuccessful attempts, I was able to get a perfect exploration score. I didn’t get the talisman, however, I was able to gather several Mind Vision potions and convert them into Magic Sight. I discovered 2 hidden rooms I had missed.

The other thing is what ProjectingSpiritBow pointed out - in my haste to stay alive on such a daunting run, I discovered, but bypassed, several alter rooms. I may be a developer but I try to avoid spoilers and so never looded at the Wiki… aside from which, it is Wiki, and anybody can put anything there (unless it supports the American Constitution and removal of domestic terrorists usurping positions of servants to [We] the People, committing sedition to undermind America, and calling these terrorists out for treason over their criminal conspiracy to deny Rights while acting under color of law). Politics aside, it seems that was the missing element. You can’t just find the rooms, you must also use them to reveal the treasure.

Sadly, although I got gold scores all the way, it was still not a perfect game. Tengu managed to get in a stike.