Yeah, there sometimes is a matchup-dependent rock/paper/scissors feel to the game, but Netrunner has so many different lines that it's possible to overcome a bad matchup. I was watching a stream from Worlds last weekend and I was telling everyone in Twitch chat how a taggy NBN deck had no chance against the Shaper with Misdirection and Clot, but I was forced to eat my words when it happened on stream.
People already mentioned Ben Ni's legacy tournament (I hope he does another one at some point), and TheBigBoy's learning decks (which aren't necessarily duelling decks, but they're balanced against each other), but if you keep checking this forum, there's someone who frequently organises a league on jinteki.net using thebigboy's decks. I think the last one finished a couple weeks ago, so I assume there'll be another one coming soon.
Some people have mentioned that those decks are no longer legal due to to rotation, but of course that doesn't matter at all, as rotated cards are still fine for casual play - it's only in tournaments that they're illegal. What it does mean is that those packs might be harder to find because I assume FFG won't keep reprinting them. But there's still stock in lots of stores, and they're discounting them to clear them, so keep an eye out. Also, the occasional person selling their used collection keeps popping up on Facebook, the BGG trading forums, and ebay.
What IS still in print and you can find pretty easily is Chris Dyer's 2016 World Champion decks. (even though a bunch of cards in them have also rotated) They weren't built as duelling decks, they were just the decks he won worlds with, but it just happens that the matchup between them is very even and very skilltesting. A lot of people hated that period in the meta because there was a clear best deck on each side and it was monotonous, but those decks were honed and perfected to face each other so playing that matchup is kind of like a self-contained game in itself!