This is my experience with this game:
First try: fighter, don't remember if died on floor 6 or deeper.
Second try: mage, gone deeper than fighter, died for some stupid moves (and dunno if it's a bug, sometimes i was unable to cast some spells, or maybe was due to a status i dind't notice).
Third try: rogue. Win with no difficulties... I had 2 invisible (second found somewhere deep, great to backstab and to escape everything), duplicate (great to take on spirits or what is their name and slow down enemies if needed), fireball (dind't hurt to have this, but did hurt enemies
) and sleep (userful for enemy control, overpowered since enemies DIND'T wake up after being hit). I also had heal in backpack, maybe i've used it once and i don't remember if i used a health potion...
Maybe i jut got lucky since i'm not a good player.:
PS: i've tried the demo of the sequel... Somewhat it has lost immediacy, but at least it seems deeper.