A minimap of each square discovered on a current level would be nice. Also, some more tooltip type information, especially for enemies. What's the monsters name? HP? Attributes? What's it weak or strong against. How much and how does rarity matter?
Home Base upgrade system. Blacksmith to build/upgrade gear. Mystic/Enchanter to buff your gear. Perhaps class trainers that can upgrade skill books.
More gear options: Something as simple as Weapon, Armor, Accessory, Boots would be fine, though 5 seems like a magic number in something like this, to me, so maybe Weapon, Armor, Amulet, Trinket/Relic and Boots could be cool. You could have boots come with implicit move speed mods and get rid of the move speed skill book.
At any rate, I think you have a very solid basis for something truly awesome here and I can't wait to see where you take it. If you need someone to bounce ideas off of I love doing this kind of stuff so you can inbox me if you liked my take on anything. Great job so far! :)
Some reiterations of features that NEED to be implemented:
Stacking is an absolute must. My dudes are all around level 110 and I have so many heal scrolls and other consumables now that I can't even get to new skill books I purchase without just wasting a bunch.
A class system will definitely go a long way towards adding depth as well as replayability and I really like the idea of a tiered class system where branching advancement paths open up at certain level plateaus. Sprite changes with each upgrade because I'm vain as well as new skill books that unlock with your advancement. Probably should also implement different gear for each class but that isn't as important within the system you've created
For the Raids: I think there need to be larger drop tables from the bosses, and even maybe some specific raid trash drops could be implemented. This would be more important if you made more gear slots (Which I think you should.) If more loot is implemented I think it'd only make sense to have the boss maybe drop a little extra loot. 2-3 pieces(with additional chances at trash loot) sounds nice for an 8man raid team.
Farm Maps: I think an interesting idea with the farm maps would be to have each of them specialized in an area. Say you have ones that are specifically amazing for experience gain, or gold gain. One that drops potions more frequently(any of the consumables really). One that even drops pre-raid gear or has a chance to drop a special/secret item or skillbook that's better or different than raid gear but is maybe super rare. Perhaps an eventual crafting or enchanting system has materials come from various maps. You could tie whatever the drops happen to be into the map thematically. For example, have an alchemy lab map and that place has a 20% higher chance at the aforementioned potion drops. Whatever the case, you could allow the maps to let the player focus on what area they want to work on. The possibilities here are endless.
Some fresh suggestion, as most of what I see here has been repeated ad nauseam:
Floating Combat Text: In the way you have "1 hit, 1 heal" etc that shows your chain of ability usage, either have it show the damage/healing done, so that you can gauge how much of an upgrade a level up or an item are or(and) show the experience/gold gained per kill so you don't have to eyeball the gain up in the top right corner each time you kill a mob on a new map which would let you know which are more efficient for what you're trying to accomplish. You could probably have this as an option so people could opt into as little or as much information as they prefer.
Shop Keep: Just have him be there permanently and unlock after like level 5 or 10 or something. His randomness is annoying, always, and confusing at first.
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