Level 0 (Wizzrobe's House):
One small thing, is the Rupee at the end supposed to be in the chest? I see the Flag 10 there which suggests that's the case, but when playing it initially I thought it was (plotwise) taken out of the open chest for some reason. I was also intrigued by the locked chest, because the tile is a boss key chest and unopenable, which is mysterious. And that's cool, but it could leave the player thinking they need to come back and bomb everything later to find something they've missed, and being disappointed when they don't find anything. It doesn't really matter either way, just a first impression thing.
Level 1 (Wyvern Cavern):
A small idea here, feel free to ignore. A new player familiar with Z1 might also get the impression that the ladder is going to be the dungeon item as they traverse the dungeon, and I wonder if there's any way you could hint that that might be the case, or otherwise play with the player's head using design to further engender that response. Thinking of raocow in particular, I don't think he has much idea of what can be done in this engine, so I think every opportunity at creating and subverting player expectations should be taken.
I like the use of ringleaders that are differently-coloured or harder enemies. It works as a simple visual gimmick to break up monotony a bit. I also think that it encourages the player later on to pursue the boss strategy of attacking Aquamentus first rather than the smaller enemies, because other rooms set up that expectation.
About the final boss, I think it's great. It's standard Zelda 1 clashing with the "new" ability to jump, and the added enemies and shots encourage the player to get friendly with the Feather to keep off the ground, which I think is the optimal strategy.
I do think a couple bats would be good in the sideview section, probably in the second room, just to break up monotony. Getting used to sideview platforming is important, and rooms with no enemies to break up action are great, but it's a little dry.
Setting "Never Returns After Death" on the Fire Gleeok enemy type would be kind. Obviously this depends on whether or not someone else used one and wants them to come back from the grave... but I think that would be a design fault. Realizing that both of these guys come back to life is a frustration that diminishes the value of the Heart Container. My two cents.
One more small thing re: warps and the name of the dungeon appearing all the time. There's a flag in DMaps ("Always Display Intro String") that makes it so that the text only appears the very first time you enter the DMap. I personally have this turned off in Level 7, and chose to reiterate the title of the dungeon above the minimap instead. Up to you -- although it would also be good to discuss whether we all want to do small things like this for the sake of visual consistency.
I don't know who created their dungeon first, but was it intentional to give Level 1 and Level 2 the same CSet? I don't thinkkk so. I don't think it's a problem, and in fact I think it can serve to subtly reassure the player that they're welcome to beat levels 1 and 2 in whatever order they like. But they do feel a little same-y.
Level 2 (Tar Pits)
The bomb hint is good. It's missing a period if you are the sort of person to care.
I had to open up the quest editor to realize that the dark room was a dark room, rather than just a Guy room with no Guy. Now, getting this across would also be accomplished by bumping into one of the blocks and saying, "oh, wait a moment, there's something here" which I didn't do, because I went straight for the doors. It's okay as-is, but if you want to "fix it" I think you can just change the walls and doors to the same CSet as the other combos. Of course, maybe you intend for it to look like an empty Guy room, and if that's the case then I salute you, because it is funny that way if you discover the secret afterwards.
Another dark room bit, and this is more of a bug. If you push the block on the right leftwards before pushing the other block, and keep pushing it leftwards, instead of stopping like you might expect it actually ABSORBS the other block and keeps going. I am going to guess that this is probably not intended behaviour. You can reset it by leaving the room, but it's probably cooler to fix it in ZQuest.
The shop is amusing, but I think it encourages the player to waste their money on bombs when they're about to encounter an unlimited supply in the boss room. If it's anything like Z1, at this point the player is probably rationing their rupees, but if they have low bombs (and since they likely know the boss is coming up) they'll feel justified on filling up. Leaving this shop to just hearts would be cool, but it also strikes me as a good spot to sell the Blue Candle -- player sees a dark room, player splurges on candle and backtracks, player gets use out of the purchase right away and gets reimbursed on part of the price.
The boss is very good. I love the initial confusion when you drop a bomb like a normal Dodongo, and it shoots a ton of fire at you instead of being hurt. The previous Dodongo encounter helps to set that up as well. (Small note, I think that Dodongo should drop a bomb on death since you can get in from the other side.) But when you figure out that you need to stick in a bomb on his fire breath, my personal experience was that it was unclear you had to slash him, and kept feeding him bombs for ages. This loses the player nothing but time since they have infinite bombs, but that also means there's nothing to stop a dummy (i.e. me) from doing it forever. If possible, changing his colour when he's stunned would make it clear, since that would differentiate his behaviour from that of normal BS Dodongos.