Depending on how far you want to go. Hronek was 2016 so if you go even bit further and take lets say last ten years you can also add Kubalik, Vanecek and Vejmelka plus add undrafted Kampf. And Kase and Simon, who are not in the NHL anymore but had 200+ games played, so thats a decent amount.
As for first round flops I would say that so far only Zboril and Kaut are flops. Other guys are still activelly playing and even Zadina can still turn in around and be at least NHL regular. But Hertl, Pasta, Necas, Vrana are top players and Zacha, Chytil are slowly becoming ones too, Faksa also has his solid place in the NHL.
But agree that compared to the number of picks we had and swiss had in the last ten years, it should have definitely be much more guys from our side.
Still I am an optimist and if I do not count first round picks from recent years there is a bunch of guys who can make it. Dostal, Lauko, Blumel, Rousek, Svozil, Brabenec, Sapovaliv, Spacek, Hrabal, Dvorak .... so maybe it will get better in the following years
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As always with czech hockey in the last 15 or so years, all we can do is hope that it will get better lol