Magmarite Mines (mostly finished except the boss) is another one I have mixed feelings on. There sure was a heavy reliance on constantly switching between items. (By this point in the game, I've also taken to setting up the cane at the start of rooms.) And with pegasus seeds, you can't even use EX/L/R. I reeeeally think you should strongly consider letting players equip 4 items at a time instead of 2.
This is another dungeon where it's way too complex for its own good and most of the challenge is remembering which of the paths that you've already been through have loose ends available now. This was not fun. A spacebar map would have helped at least a bit...the sidescrolling bits mean it wouldn't have fixed everything, but god, it needed everything it could get and the passive map was absolutely not up to snuff even a little. This is the first dungeon where I actually threw up my hands and just made my own map, and I hate that I felt the need to do that. (The thing that tripped me up wound up not being an obscure staircase, but me failing to realize that I could hit a certain pillar from the vantage points I already had available. I think this was a clever trick, but also one where I only figured it out because I was looking at my map and didn't have to walk to that one screen first before thinking it over.)
I liked the unique things about it, and I do feel like I'd have enjoyed the dungeon a lot if the navigation pains weren't so bad. (Both the lack of a map, and also just...transit in general. Even when I made a map it still took ages to figure out where to go and then go there, because there's like a dozen different pairs of staircases.) Dungeon item seems very powerful, but interesting.
There's a certain section I didn't see coming and I thought it was a really cool twist. (Incidentally, it took me ages to figure out what item to use to start that section--I kept trying to use bombs, and I feel like that should have worked too.) I do think the block puzzle was a bit complex for it. It's a perfectly good puzzle, but in practice, I took one look at it, paused the game, took a screenshot and made absolutely sure that my solution would work. And that kind of took me out of the action. Also I'm a little disappointed that I never got to re-explore the southeast, after leaving my mark on it.
(I finished that section late at night, and since I was low on health after it I decided to just restart and come back later. It was a bitch and a half to find that part of the dungeon a second time, and re-finding it doesn't seem to have actually helped, and I was slightly bitter about this.)
It's still unclear to me what lighting all the torches in that one room actually did.
There's a quirk in the sidescrolling sections where it's very hard to line yourself up properly with a ladder when there's walls around it on both sides. This isn't the only place where it's been a problem, but it's definitely more prominent here.
Aaaaaaaaaaaaaand once again, the trek to the boss room takes forever and contains multiple kill all enemies rooms that reset every time. This time I only damaged it once before it killed me, and I'm already dreading the next attempt. This is the kind of thing where I'd be fine with the difficulty if I could just fight the damn boss, but adding the long walk to get there feels unreasonably punishing.