Great game with good replayability. Each class has a couple of really strong combos which makes it fun to try out each one.
Some thoughts around balance:
-Regular runes aren't great, They seem too expensive to buy and as rewards I found myself just selling them immediately and only ever buying/equiping the unique items.
-Necromancer items don't always seem to propogate to skeletons (e.g poison rune doesn't apply to summons)
-It would be good to have a "pay to refresh shop" so you can search for specific items.
-Might be interesting to add non-combat encounters. E.g wandering shop, choose an upgrade
-It would be good to add a stat that reduces the time it takes to respawn a new unit so you could add more strategies like spamming 1mana warriors and priests