I like these ideas but I do have one thing to criticize (please don't hate me for being negative, I'm just trying to help) I think the towers should be more strategic. The archers are perfect, there is one for doing physical damage against strong magic resistant enemies, and one that's fast for lots of armored enemies or flyers. However, the mages seem like they both serve the same purpose, one of them has an instant kill for singular foes but also has guards to stalk multiple enemies and the other tower also has skills for many armored foes.
If I might make a suggestion to this, maybe you could have these Mage towers instead:
Pentagon Tower (for a singular strong enemy)
A Demon Overlord who summons a red pentagon that fires a constant beam of red death energy from the underworld.
Range: Great
Damage: 15 magic damage per quarter second
Attack speed: 3 seconds to charge up the laser, must charge again for each new enemy.
Death Energy: (250/250/250 gold) As the laser continues to hit the same target, the damage increases by 1/2/3 points each quarter second, but cannot reach more than 51 per hit.
Cursed Beam: (250/150/150) Any enemy who is being struck by the beam is slowed by 20/35/50% of their speed.
Orc Mages (For multiple armored enemies, but crowd control is still inferior to artillery)
A green Orc Mage who shoots 2 green bolts of magic. The bolts don't hit the same enemy unless there are more bolts than enemies.
Range: Great
Damage: 25-40 per magic bolt
Attack speed: Slow
Bolt Swarm (200/200/200 gold): Increases the bolts fired per shot to 3/4/5.
Supercharge: (300/200/200 gold): Every 8 seconds, fires a single green bolt of magic that explodes for 80/140/240 area damage.
Also, I think the Saurian Coils is a bit OP and not as strategic, but the bandits are great.