Well, it took me (checks) three and a half weeks, but I'm back and excited to get back on the Ocarina of Time horse! Gonna have to break this reply over two comments:
gameplay diary
Okay, since I ended up writing this waaaaay later it's unfortunately going to be lacking in a lot of detail, but I'll do my best:
After entering the water temple, I flailed around ineffectively for a good 20 minutes or so before even finding Ruto and changing the water level for the first time...I can definitely see how kids would have gotten completely lost in this place. I think I accomplished nothing on the first cycle of water level changes, but after that I started keeping careful notes, with a section for each level and four subsections for each cardinal direction, flagging things that I should return to once the water was at a certain level or once I received some new equipment (which I'd later discover was the longshot!). Once I got into a groove, I got through the temple fairly smoothly, I'd say. However, I think a major reason why I made smooth progress was the quality-of-life upgrade of being able to toggle the Iron Boots on the fly. Not only did that make the process much less painful, it also enabled techniques I'm sure the developers never intended such as feathering the boots on and off to travel in a straight line through the water, which definitely made light work of some obstacles (although no sequence breaks or anything like that).
With Dark Link, I realized what the fight was a moment before it actually happened—beyond the general vibe, I think the room also reminded me of the boss room for that same fight in Zelda II, which is one of the only parts of that game I've actually seen. After the requisite ineffectual flailing and taking a bunch of Peter Pan flip kicks off the Master Sword straight to the kisser, I eventually settled on blocking and then immediately attacking with a jump slash, which seemed fairly consistent and made pretty short work of him. But even then, he still took 11 hearts off of me! I didn't end up needing a fairy, in the end, but it was a close shave.
The final boss had a really great and scary intro cinematic—felt like something out of Alien or something! It's really amazing how games like Ocarina of Time and Metal Gear Solid (from what I've seen and heard) innovated on the use of cinematic language in video games. I was just reading earlier today in Super Nintendo (new book from Keza MacDonald that's a cultural history of Nintendo's biggest franchises—pretty good read so far!) that the use of in-game cinematics as opposed to pre-rendered cutscenes was not so much a conscious aesthetic choice as it was a necessity due to how much the game was changing right up until its release; I'm glad it ended up that way because pre-rendered cutscenes would not have aged nearly as gracefully, and even when well-executed I found they kind of took me out of things...glad we've generally moved past FMVs, as important as they were during the transition to full 3D games.
Anyway, as for the actual fight, I'm not entirely sure I approached it in the intended way since I basically never stepped on the central four pillars other than to start the fight, but I basically just stayed out of range and spammed the longshot so I could get in a few hits here and there. Did get flung about three times, though.
After finishing the temple, I immediately looked through my notes and hit the spots that I thought I could use the longshot. First, I hopped onto that roof in Kakariko to talk to the poor fella who's been stuck on the roof for seven years (Heart Piece Get!!), and then I clambered up onto the upper floor of the windmill. I was a bit confused, though—I assumed the purpose was to stunt on the guy who's on the watchtower and mentions that he can't stand anyone being higher than him. I grabbed the Cucco and flew at him a few times, but his dialogue never changed...am I barking up the wrong tree? Is there some other way to get higher than him to trigger an event, or is his dialogue purely flavor to call back to him standing on the balcony in Hyrule Castle Town? I couldn't really see a use for the Cucco (beyond fun) otherwise, since you can longshot directly to the aforementioned roof.
In a subsequent brief play session, after learning the Bolero of Fire (...definitely could have saved myself a lot of time if I'd done this earlier—was it really as simple as just talking to the kid again after getting the Goron Tunic? Or did I just miss/ignore that the first time I talked to him?), I headed over to Gerudo Valley and Longshot my way across the broken bridge. After immediately getting spotted by a guard and breaking out of prison, I started very clumsily exploring the fortress, getting spotted a whoooole bunch of times and cheesing some guards with Longshot spam. The Biggoron Sword made short work of the Gerudo warriors, but it was only after rescuing three of the four carpenters that I realized I could knock out the guards with arrows! On my next play session, I'll hopefully find that elusive fourth prisoner and see where things go from there.