Evidently no one else has done these still, otherwise you would have found that Wicked 11 can be done with only 8 skills. 
For that level, I actually did have a look at it last week but didn't find a better solution at the time.
I really don't have the time to do nothing but solve levels all day. I already am doing it more often than I should, during times when I should be working.
So there are still levels from original Lemmings on this challenge thread and possibly earlier ones, that I haven't really took a hard look at yet. And even if I did, it might not be a hard enough look, just like you didn't report 8 the first time for that level.
But, I did improve today on a level you've done earlier:
And the second half of Blitz:
9: 21
As you suspected, it was improvable, to 20 skills. Actually you're very very close; I think you would've gotten it had you realize when exactly diggers turn to fallers (you solution seems to indicate you think they fall one pixel sooner than they actually do).
But for an extra challenge, I've made my 20-skills solution for Blitz 9 save 100% as well. This is not as trivial as it seems, because of the spacing between your blocker and the lemming that frees the blocker. In my solution, not only do you need to find the right place to block and the right place to release the blocker, it even influences one of the actions of the trailblazer. Try it out yourself first w/o looking at the replay to see what I mean.
