The 0.2 demo is interesting. Over all I think it is a promising concept with high potential.
Critiques (with suggested fixes):
-It may be good to add a system that will populate the rooms with enemies based on how many minions the player already has. More then once I found myself entering a first room and fighting 4 monsters including 2 lips monsters with only 3 minions. Not the funnest thing ever.
-I don't know if you already have this, but in your random room generation it may be good to have the portal appear in a location that has the player feeling like they had to fight to find it, but not so far that if they want to stay on the level they don't feel like they have to backtrack for half an hour. (not that there is any incentive to stay on a level in the current build. )
-I recommend making the cool-down for the melee attack something you can see right next to the player or more visibly on the cursor, ideally not a UI element but rather a part of the game. (no one is looking at the corner of the screen to see how much longer they have with a cool-down that is 1 second long.)
-When populating a room once or twice I found monsters spawning close enough to me that they dealt damage almost instantly. Perhaps a delay in time before damage can be done, or smart spawning that will force monsters to spawn a safe distance away from the player.
-Passing through the portal feels like no progress has been made except for the words that say I'm in "Dungeon 2" I would much rather have something in game, like the environment, demonstrating how far I am and changing with each level. (but maybe it does change more and I just suck to much to get that far, but you still want people to see progress right from the start.)
- have the minions already spawned in the room and you have to stand close to them or pass over them to get them to fallow you, this could add the the story as well as have it make more sense then them popping out of the air when a room is cleared.
-click and drag minion positions? For when you have lots of them and you want to make a wall.
-You could give the monsters a long cool down before they attack allowing the player to come up with positions for the minions before the fight. Or a distance that the player must be in before the monster attacks.
-minion merging for stronger minions?
-monster re-spawning in rooms you have already been in? Maybe have vents or tunnels that suggest they could have come from there.
-buttons or other things that the player can send their minions to activate, opening doors or springing traps.
-pre-chosen formations that the player can commend the minions to stand in
Like I said, there is a lot of potential in this concept. Sorry for making this 5 miles long, but hey, you said you wanted feedback. :)