Yea mage can be kind of overpowered, seems like you can just sit at one level on one side of the map, spam fireballs, and they seem to just walk right into them and then you command your teammates to protect you and you just sit there and rack up a ton of kills with no deaths. Decent game, though.
First I think you should just plain drop the coin collecting because you can't move your troops around at the same time. Second I think you should give half or quarter xp for battles you've fought already or to give xp to units that weren't in the inital battle, mainly because I hate looking at unsymmetrical units. Third It'd be nice if you could plan where each unit moves when you set up their location because it's too hectic doing it all when the battle has already started and would incorporate more tactics to each skirmish. For a sequel I'd recommend a smarter way of moving the units or make it so they automatically walk around obstacles, It isn't a major thing but would be easier to have everyone where you want them. Lovely game.
A great idea for this would be to make a single character rpg using all the classes here, you could add more equipment, skills, weapons, stats, minigames, cosmetics and if you really want to make a high quality game, different storylines for the classes, I just came up with four right off the top of my head lol. I know it would take a while but I can basically gaurentee It'll be a hit, n there would certainly be ways to make money off of it. Like if you agree :D