Secret Paladin isn't as good as people think; only because tempostorm rated it on the first place on wild doesn't mean it's broken. N'zoth Priest destroys secret paladin, as do Patron Warrior and Freeze Mage. Heck, i now even easily won with my Zoolock against a Secret paladin an hour ago.
there is no deck that "destroys it"... there are few decks that are favoured against it but you can still easily lose with those decks. Ive lost numerous time with nzoth patron or even freeze mage against secret paladin since if they get the god curve and you dont have the needed answers at the right times you will get steamrolled.
The main problem that I have with that retarded deck is that its stupidly easy to play while being ridiculously strong. I never had problem with prenerf patron being the best deck since the noobs were bad at it and they couldnt just faceroll with it to legend. Decks like secret retardin in wild and midrange shaman in standard which is also a autopilot deck should finally get nerfed in the oblivion.
You can lose as Freeze mage with poor draw against god draw but that's always a possibility when playing Freeze. I haven't tracked my winrate against them but the seasons I've played at high ranks/legend in wild I get excited whenever I see a paladin because it's usually a free win. They play a lot of sticky but low power minions, they can't deal with doomsayers, and they can't deal damage from hand. It's a Freeze mage player's dream. As a side not, the only reason Freeze mage isn't completely busted in wild is that people run eater of secrets to counter secret palas.
Unless Secret Paladin is addressed, Wild is not viable in the long term.
I don't know what your definition of "viable" exactly is but Wild is broken, it always was and thats what it is intended to be.
It's literally the sink every broken card that didn't happen to get nerfed ends up eventually, it's not meant to be an competitive enviroment and it's not meant to be balanced, thats what Standard was established for. Wild is the place you go if you do not care about all of those things and want to toy around with cards not in the rotation anymore.
Unless Blizzard someday introduces a third format akin to what "Modern" is in MTG that won't change.
To be fair, even Legacy and Vintage are heavily regulated. Both Chalice of the Void, Treasure Cruise and Lodestone Golem have been restricted and Gifts Ungiven has been unrestricted within the last year of Vintage. And that format is so broken (even more broken than Miniature Warfare) and not taken serious by anyone. EDH are also regulated even though being 100% a casual format.
It is possible to have a format that's both broken, casual and balanced at the same time. The power level of a format says nothing about the balancing issues. Why wouldn't it be a good idea to try to make a format fun for everyone?
Secret Paladin is still disgusting.