This game is quite fun but there are some complaints: One would be that in Diablo, which you said this game emulates, you can hold the shift key while attacking and that causes you to be able to attack wherever your mouse is instead of attacking a target. This is especially useful when using a ranged unit. Especially one that can attack in a large area with multiple projectiles ;]. The point of multi-arrow in other games is to spread out damage not necessarily to deal heavy damage to one target.
Another complaint would be that you could have come up with more creative names for the weapons and armor.
Another complaint is that, after a few levels, you don't die. Even if you do die, there's no penalty. You should have an experience penalty or at least a money penalty. I'm saying that the game is too easy. There needs to be a threat.
Another complaint is that there is entirely too much equipment that gets dropped and not enough things to spend your money on. I never had to buy potions but I was going back to the store ever 3 to 5 minutes with a full pack full of crap. A little more balance there would have been appreciated.
Also, you should have made passive abilities. For example, the pierce arrow should have been a passive ability that, as leveled up, increases the odds that the arrow will pierce not the damage done. The damage should be solely dependent the archers attack and whatever ability. Being as the archer is the only one I used I can't really advise on any others but some passive abilities would have been great. Maybe for the warrior they could have a natural element resistance passive ability or a death stack ability like a bloodlust of sorts and for the mage you could have had chances of instant death for certain spells. I.e. fire could have an incinerate chance.
This is in no means a bad game but there's certainly a lot that could have been improved on.
---------- 3/5 -----------