We're not. Based on how you wrote it you made it look like you meant that every level of LWT is easier than SEB Lems
Well, to be fair, I now realize there are two ways to understand the statement "every level in LWT is easier than the entirety of SEB Lems":
1) "the entirety" like "every single level in that pack is harder" (which we agree is not true, and which I never meant to imply)
2) "the entirety" like "the entire pack", and the difficulty of the entire pack is determined by how hard it is to beat the pack as a whole. Because a single super-hard level, even if every other one is easy, can stop you from completing a pack. And completing the pack is simply much harder to do with SEB Lems than with LWT.
Welp, I solved it so I guess the hint won't be needed after all, only for me to see you post the hint anyways. Thanks for helping. 
I'll reveal my full feelings on this level when I show off my solution on video, but fair warning: I raged a lot on this level and the solution should NOT have taken this long.
First of all: Congratulations for solving it even all by yourself, Arty! 
For the second part: Of course, I'll have to actually see your solution first before I can confirm whether it's actually the intended one, and if so, to what extent. My own replay was fairly precise, but I've seen replays by others where the setup of the same core trick was less precise, because it relied on fewer moving parts. As a consequence, I had less of a bad conscience about it, because I discovered that easier things than what I had in mind originally were possible, and I had no intention of breaking those slightly alternative approaches.
Maybe you're the first one who actually did what I did when I made the level - or
maybe you've even done something that's even harder to pull off. I have no way to tell yet. 
That said, it's the final main rank, so just like in other packs, if there are supposed to be any levels where no punches are being pulled anymore, it's here. 
Sure, ideally that difficulty should be conceptual more so than pixel-precision, and definitely not based on execution difficulty alone. But avoiding pixel precision is usually no longer as much of a concern on levels from the final rank of any pack if the solution necessitates that precision from a conceptual standpoint.
Which is why I'm a little confused about this statement of yours:
I saw the solution pretty much instantly
What do you mean by "instantly"? 
As soon as you started your next session of attempting it?Because I'm pretty sure you didn't see the solution conceptually right away when you first looked at the level - otherwise you probably wouldn't have asked for a hint...
Unless this is another case of what happened on Legend 04: That your first instinct was the correct one and you discarded it because you couldn't execute it.
That's always a pity, because rediscovering the correct solution if you've already had it and discarding it is harder than discovering it for the first time.
In terms of "making destructive skills go through in general": I think now we've seen two different examples of how inspiration by other players can easily create monsters accidentally ^^:
- in my first pack Paralems, I had some hidden objects and a couple execution-heavy levels. Then WillLem came along with his first pack(s) and took that to even greater extremes than I would ever have imagined possible.
- in SubLems, in turn, Arty had some of these levels making skills go through each other. That inspired me to make my own, and I've taken that to much larger extremes.
The special challenge with Legend 04 was probably that this was the only combination of destructive skills of which Arty wasn't aware / sure (or at least not anymore) whether it would work in the first place: Miners crossing, Basher and Digger crossing, those were clear because he used them in SubLems himself. When I once asked about these combinations while I was playing SubLems, I also learned in turn that making a Miner and a Digger pass through each other is
not possible.
That said, in terms of execution, I had to get these levels right myself - just knowing the solution on a conceptual level is not an advantage in this regard - and if it had frustrated me enough, I obviously wouldn't have included them. In turn, I was also frustrated by some of the levels in SEB Lems which required this "Miner-goes-through" stuff with a lot of setup. It's simply part and parcel of this type of solution: Often a strong limitation of destructive skills is required to even enforce the necessity of making a Miner go through in the first place. Which then becomes precise because Builder staircases are fairly thin, and it's easy for at least one of them to be accidentally cut through by the Miner.
I remember kaywhyn having similar criticism about Legend 04 as you, but for Legend 07, while he mentioned the pixel precision, too, he still called it a "very nicely designed level" overall.
IchoTolot meanwhile had trouble with the crowd containment on Level 04, so that's what he criticised, but I didn't see any criticism of skill crossings in his comments.
Only about lightning traps hidden in clouds ^^, which in turn Arty fortunately appreciated (on Legend 06
), because he understood the flavour reasons. You know that when in doubt, flavour trumps mechanical fairness for me.
As I said under Arty's video, I always considered the Miner's position on Legend 04 fixed, so I didn't think positional cues in the terrain of what to assign where would help. The issue is
when you assign the skills (i.e. to which lemming from which crowd), more so than
where. Depending on when you start mining and with which lemming, even if from the same position, that will inevitably influence how you have to make the second assignment. That is the inevitable challenge of levels relying on relative timing between lemmings.
Finally, just because terrain cues are there doesn't mean they're understood by the player as such.
I've repeatedly missed them on levels from SEB Lems that required skills going through, for example, and just mistook them for arbitrarily-placed decoration. Unless it's explicitly written as "Mine/Bash etc. here", like in the Practice levels of Lemmings 3D, it can easily happen that the only person who understands that terrain piece X is a position cue is the level designer him- or herself.
With Legend 07, I don't think terrain cues would help that much to begin with, because again the relative timing is the issue. But I'll have to see Arty's solution first before I can confirm whether it's actually the intended one to begin with. I assume it relies on the main trick, but the intended / alternative question is all about how that main trick is set up.
