I'm not sure I agree with the idea that they're not seeing play, and if they aren't then it has more to do with the decks surrounding the cards than anything else. All the cards you listed except the Tekahn stuff are currently mainstays in tier 1 wild decks, every single one of them, even the neophytes (though maybe not the robes). If they're not working in standard, the reason has nothing to do with the cards themselves but the decks they belong in. They are flourishing in supremely effective decks in wild at least.
I'm not sure I agree with the idea that they're not seeing play, and if they aren't then it has more to do with the decks surrounding the cards than anything else. All the cards you listed except the Tekahn stuff are currently mainstays in tier 1 wild decks, every single one of them, even the neophytes (though maybe not the robes). If they're not working in standard, the reason has nothing to do with the cards themselves but the decks they belong in. They are flourishing in supremely effective decks in wild at least.