Is it just me, or does this game seem fantastically unbalanced, at least at lower levels?

My Archer is fast, has good ranged attacks, including one that semi-reliably shoots around corners and that don't use mana, so she only infrequently takes damage, deals out plenty, and levels her skills up easily. Everyone else has to use limited mana to use their specials and level up their skills, or else is melee focused so they constantly take damage whenever they're dealing it out. Up through about the level 7 dungeon now, and it's so lopsided that I've stopped playing any of the characters but Archer and Rogue, who also uses a bow, and swaps the two Archery Air skills in before every expedition.

I'm assuming this strategy will come back to bite me at some point, but playing any of the other characters is just dull; they get to use their spells 2-3 times per adventure, and after that they're just vastly inferior Archers.

You can find gems with a +Mana on Kill effect, which reduces and will eventually completely eliminate any mana issues for characters with decent to high Intelligence stats.

Even without that though, you should be drowning in mana potions and water bottles to use.