The exp on the evil eye tower seems to be a little off. cant seem to get one to level all the way up to max level during a normal game even with it right at the front and hitting every mob on its way in. I do have maxed demon tree.
If you still have troubles, keep the missle launchers built up until you have about 200 minerals right before the motherships, then after you knock out about half of them or run out of minerals, sell one of the missle launchers to feed the others
minus one missle launcher, put up two repair stations or as many as you can afford near where the ship will be, a slight bit of luck is needed to ensure that you knock out one or two mother ships off the back, and you will need one more solar station or an upgraded energy store
If this is your first game then nice little prototype. Gave 2/5 because of how basic. The guys do spawn in almost the exact same spot although a different order. Keep up the work and dont be afraid to test new things.
The lineup I use to beat every cave is Witch, Centaur, Dwarves, Mermaid, Succubus, Phantom Armor. Spells: Comet strike, Healing, Zeus Wrath, Athena Protection, Phoenix Strike, Ice Trap. Don't attack bosses until zeus and athena is up, dont use phoenix on cave 5.
To beat cave five: Use all ranged units and demon armor. Must have mermaids and archers at a minimum. If you dont have them, beat with more heros. Do not use magic cannon. Use Comet, Healing, Zeus (or hercules if you dont have it) Athena, Ice trap. First comet thats up use it to pull the other hero. When all units but dwarvs spawn, hit all forward and spam it. Right before your units hit the invisible goblin, use Athena and Zeus. Ice trap when they fade. If everything is upgraded, you will win.