Wow, you guys actually played the original LoZ as children? Not surprising but I'll have to admit I feel pretty out of place here.
My first encounter with a Zelda game was the first 5 minutes of Link to the Past at the age of like...9 back in 2005 (yes, far after we were far into the 128-bit era). I couldn't even figure out how to get into Hyrule castle let alone make any progress until years later, so it's pretty humbling how you guys managed to make your way through the original Legend of Zelda at that age!
When I first played through Zelda 1 on my Collector's Edition a few years later, I didn't remember the 6th dungeon being all that hard. Save you, the difficulty of the rest of the game was so incredible for me nothing stood out as being particularly memorable aside from my hellish trek through the 8th dungeon. But oddly enough, I didn't have a hard time finding it at all. It was the 2nd or 3rd dungeon I encountered, too.
I actually find it fascinating that so many young people are interested in 8-Bit Zelda games. The fact that most of this community is under the age of thirty, is quite shocking to me.
I'm on the other end of the spectrum, and my memories of when Zelda was new and shining are quite clear and vivid. I played both quests, when the game was first released, and then waited for a rumoured a third game that never came to be; until 1991, with the release of Triforce of The Gods.
(Damn you NOE/NOA, for bastardising the title in European and American versions!)
I personally still prefer the FDS versions of Zelda no Densetsu, and Link no Bouken to either cartridge version, for better music, SFX, and of course, the lack of horrible translation errors; and I have a copy of the Beta dump, that I;ve played, but I didn't really notice that Wizrobes were less powerful. It seemed to me that the final cut was less difficult overall, with many different enemy combinations compared to the Beta that has been released.
It is clear though, that if the changes were done to make Wizrobes harder, that it wasn't a last-minute decision. The Beta dump is missing most of the second quest, and in the time that it took to develop that, I'm pretty sure that Nintendo would have noticed if changing the damage of one enemy created too high of a difficulty spike.
Really, the enemies that always gave me the most trouble, and reason to panic, were LikeLikes, and Darknuts; the occasional Patra fight, and Blue Lanmolas. The ZC version of the first and second quests are actually easier than the real game, in a few ways; so if you haven;t played the original title, try it both in ZC, and emulated, and see if you spot the difference.
We all still want to see an earlier Beta dump, with that mysterious, lost screen 'Take whichever you want', featuring either the sword, or the boomerang; if any of you recall that. 
I was always curious if the original intent of the boomerang was to damage enemies, and if the sword always had beams, in earlier versions. The FDS sword beam sound, by the way, should be in ZC somewhere. It surprises me that no-one has tried to convert that over, as the electrical sound in the FDS version is what the more familiar 'trspre', sound, from Z1 is supposed to be.
I'm not sure if I would call Level 6 difficult, in contrast to 2nd quest levels, with walk-through walls, and red bubbles, or really too difficult in general, given that you can have the magical sword, and the blue ring, by the time you get there. I think that the flaw is that the difficulty thereafter drops off a bit, making L6 seem like it should be L8.
In fact, if you transposed L6, and L8, swapping the Gleeok types, and treasures, between the two, the game would be much more balanced.
