Thank you for playing the game (and making a Youtube video of it), and thank you for the detailed feedback!
So yes, the game really does need a tutorial and that is something I am currently working on to be added in the next update (version 0.6b) to guide the player through the mechanics and flow of combat as well as the menus in the War Room where you buy equipment, upgrade stats, etc.
When it comes to the enemies, their AI is pretty simple at the moment and that's why they will currently swarm your team. This will not be the case in the coming updates as I improve the A.I. to make them less zerg-rushy.
The skills feeling useless is a good call out, and I will look into ways of making them feel more impactful or turn the tide of combat for the player. I think this is also tied to what you brought up about the difficulty and being unable to progress.
And speaking of the difficulty, that is another valid point and I will find a solution in making it more scaled and adjustable while still keeping it challenging. I was worried it might be overkill toward the player, and it looks like it is.
But thank you for taking the time to play the game and make a Youtube video out of it, and hopefully you'll enjoy the game as it nears completion! I'll be taking your feedback into consideration!