I'd like this game very much, if it wasn't so horribly unbalanced.
Health: While the character only needs 3-4 hits to dispatch an enemy (with a damage of 35-40), the enemies, while dealing like the double of that (~100 without armour equipped), need 50 hits, because the character has crazy amounts of hp. Unfair and not really fun
armour value: I tested it and found that defense is useless.
I faced one of the big bosses without any armour and the difference of that (~350 points of defense) was a meager 50 points. The same reduction of 50 points applies to attacks by all the other monsters.
The magic, specifically charge lighting: When such weak spell (in diablo) can kill bosses with one salve, You know, that it's too powerful.
To solve problems 1 and 2, I propose You don't increase all the stats at every level up, but make the surpluses of armor enchantments higher. That would lower the characters max hp/mana and give defense, protection spells and potions importance.
Against the ability to supercharge spells, add an incrementing level/stat requirement. Have the arrow spells dexterty as requirement and most of the others intelligence of course.
And 16 classes of monsters? Maybe, You meant 16 different sprites? Actually, there are only ranged, melee and if we want to count the special abilities of some poisonous attack and freezing attack, excluding the bosses and generals. ;3
And a last thing, I also encountered that 2x2 room bug. Restarting the game solves this, You keep your progress but have to fight the boss again. I think, this occurs when standing in the middle of the room, while the portal appears. (I haven't tested this.)