Hey dev,
The game is more balanced in 1.1.5. I was able to defeat the final boss without encountering any bug, at least in my playthrough. It took me awhile tho. Based on my playthrough, a few things can be improved.
1. The final boss (the skull with obsidian blocks and unknown cyan blocks) seems easier compared to any enemy in the last zone since there is actually a reliable strategies that can be used to defeat it. The random enemies in the last zone can be more difficult if luck is not on your side. More on no.2 on how I defeated the final boss.
2. IMO, the lobbed type weapons (mortar, dual mortar and grenadier) are very OP. More OP than the plasma weapons as they don't requires aiming as much. You can even leave it on auto-fire and combined with flares, they can destroyed buildings easily. I was able to face such random enemies with 5-6 grenadiers and I don't even stand a chance. This is how I cheesed the final boss btw. Slowly chipping away its shield with a single grenadier and 2 regular mortars. I think you can increase their weapon size so they would be more balanced? Up to you tho.
3. I think enemies with only flares and powerless weapons should be considered a win for the player since they can no longer fight back. What I meant by powerless weapons are weapons that required energy to use but the island is no longer capable of storing and generating energy, thus the weapons are not usable. I was able to do so on few occasions during my playthru where the enemy cannot fight back.
Glad that I was able to play IIsland of War. It was an awesome 3 hours gameplay and I'm looking forward for the next updates. Take ur time on developing the game and fixing those bugs. Thanks man!