Okay, took me a few hours of trying but I beat it:
Locking tier 2 reagents behind an upgrade seems a bit punishing and it messes with my muscle memory but it works if you want to give the player a sense of progression.
Every time I play alchemickal it takes me a while to readjust my muscle memory and remember that Ice counters electricity but not fire and electricity counters ice but not water. Took me a while to get back in the rythm.
Color coding is still off: Fire explore should be fire colored instead of red, neutral ice and water enemies are hard to distinguish when they're being summoned which can end your run if you're trying to scythe one of those neutral enemies and you realize too late that it's a cryo mine instead,
The aggressive blade enemies that charge you complement the ranged ones I don't mind them.
Turrets are fine in small rooms but in larger rooms like the boss room they can feel unfair when they're shooting from off screen. The turret rotation noise is a little grating.
New boss is cool, more fun that the old one because the old one had that multiple bouncing ray attack that was hard to dodge.

This type of room is satan incarnate and it was responsible for most of my failed runs.
I think you've got a room balance problem on your hands: The ones with pillars you can move around are super easy, the ones with small pockets you can hide in are also more forgiving, the other ones feel completely different and so much harder especially in the upper floor where you have no room to maneuver and doge the initial attack by the whole wave of watchers.
Difficulty-wise I kept drying to pits, self damage, mines and barrels instead of enemy attacks. Once I unlocked tier 2 I started using steam + electricity + ice and that's a combo that clears rooms of all enemies fairly easily. I never felt the need of experimenting or mixing my tactics unless there were a couple of enemies left to speed things up.
idk if it's even viable to use anything but revolver + AoE mix on hard.
Still very fun and the new enemies added some nice variety to the rooms.