They said it couldn't be done, but I think I've come up with a way to change Oh My Yogg! that doesn't destroy the card.
Secret: When your opponent casts a spell, Counter it and you take damage equal to the spell's Cost.
Because it never causes the spell to actually work against you (the Paladin's opponent), this makes it much less frustrating to play around, especially when you have only high-cost spells in your hand, but it still disrupts what you were actually trying to do. I think this effect is much more in line with what a 1-Cost Secret should be capable of.
I saw someone suggesting to make it so that when your opponent casts a spell, you cast a random spell of that cost. It's still yogg-related but becomes a meme card only. Making the spell you cast cost x more than the one opponent cast could make the card more usefull maybe.
The idea sounds interesting to me, but I get that it would probably kill the card and Blizzard almost surely won't do it.
Swap card from Paladin to Mage class (which identity-wise tends to be much more Yogg/RNG related), make it 3 mana to be in line with the other mage secrets, move Counterspell to Classic, HOF or whatever (so it's "replaced" by Oh my Yogg) and give Paladin a more crusadery/not so lunatic secret, such as "after your opponent casts a spell, summon one/two 1 mana cost minion and give it/them divine shield, or summon X passive hero power dudes, or even make your hero power cost 0 mana for 2 turns... I don't know, but I'd like something along that line, even if I know it will never happen.
Some random ideas: Oh my Yogg! When your opponent cast a spell: - they shuffle it in their library then cast a random spell of the same cost instead. - they cast a random spell instead. Take damage equal to its cost. *(Any cost spell) - they cast a random spell instead of the same cost then draw two cards. *(A major drawback) - they cast a random spell instead of the same cost then destroy one minion you control at random. *(A minor drawback) - they cast a random spell instead of the same cost then you discard one card at random. *(Self disruption) - it turns into a sigil then they shuffle a scroll of wonders into their deck. *(The spell becomes a Sigil so it 'activates/recasts itself' at the start of your next turn with random targets).