Yeah, I kind of forgot I did a bunch of things to make the game harder recently. I added the healing from upgrade areas, reduced healing from other sources, buffed the cube heads, and halved the player's max health all a few days before this demo. So, now I know I made it way too fucking hard, heh.
Since watching that gameplay I already increased the healing received from spent souls a bit, added a flat 15 free healing there, slowed the cube head's attacks down a bit, and lowered the number of enemies spawning in the first room.
The game gets plenty hard down the line, it doesn't need to be stupid that early.
Thanks a whole bunch for the video and feedback, I'd be pretty lost without the lovely boys in these Demo Days.