Ha, finally succeeded in clearing Twisting Passages!
Used Elf Bloodmage + Fire Heart, got lucky enough to get only one high level changeling and Mysteria Annur, kept fireballing much higher level enemies while exploring and by the time I had explored everything I was 6th level, had 100 piety, all the changelings were in 2nd mode and I had only killed about 5 enemies so there was plenty of space left.
Used mana leak, killed a couple of lower level enemies to level up and regain mana, then started fireballing Evolvia. Used mana potions and Schadenfreud potion to keep firing, used a single melee attack whenever Evolvia got the fireball counter and used lower level enemies and their blood pools to regain health when necessary.
This time mopping up the remaining enemies was easy.
I had to win one more normal dungeon to get the Bazaar level 3 quest to finally appear (and perhaps I could have gotten it if I had just kept playing the easier dungeons).
Unfortunately I can't even see Deep Swamp yet so I'll have to finish something else before finally getting the damn elite items...
But progress is progress