If I'm thinking of the right level, Top Shelf is the same level as Bipolar Maniac in the Lix community set. That one only wants a single trick to solve, but it's a very hard trick to spot, and the level offers many plausible directions to go that don't lead anywhere. I remember, when Insane Steve first built the Lix version, spending ages on it without getting anywhere. I haven't played many of the top-tier levels so maybe it doesn't belong in Armaggedon, but I definitely wouldn't drop it down lower than Carnage.
Oh No, Not Again is notorious for being one of the hardest ever levels to solve -- even people like Nepster report having taken months over it. I haven't solved it myself, but I've certainly found it an interesting level to attempt, and don't see anything wrong with it, other than dependence on time limit (and considering that RotL includes a lot of older content, probably it still has a fair number of time-limited levels?) Sadly, because of time limit dependence we may have to remove it from the Lix pack (unless we can find a good way to fix it, which isn't necessarily impossible) so it would be sad to see it cut from RotL as well.