Any classes that are worthless?  Which ones did you find effective?  My sage seems good but runs out if mana quickly on auto

<t>Question:  I'm on floor 34.  Floor 18 has the area where you use the key you get from floor 30, but 18 through 34 so far, has the bottom right corner blocked off on every level.  I unlocked it on 18 but that only led to one room on 19 and it has the portal out of the dungeon which is next to usel...