Druid and Warlock are the only classes I'd consider "overpowered" right now, but I'd also say Mage and Warrior are above Paladin in general.
Secret Paladin has been figured out, and Murlocadin is too inconsistent and slow to be top tier.
No way is Warrior above Secret Paladin.
You have been subscribing too hard to Tempostorm if you actually believe that Secret Paladin isn't at least top 2 in the game.
There's nothing to figure out about Secret Paladin. It can beat anything in the game. People don't even bother teching stuff in the deck because they can just auto pilot to win.
Murloc Paladin is easily a tier 2 deck too and Midrange Paladin and Aggro Paladin aren't far behind that either.
This is end of era state of game right now, people just don't really give a hell. Reminds me of when people thought Grim Patron was figured out because Control Warrior and Handlock were tier 1. A couple of non good match ups is not enough to put down that deck.
If I had to make a tier list it's pretty simple for me:
Tier 1 (aka you either play this or you play its counters)
Midrange Combo Druid
Secret Paladin
Zoolock
Tier 2 (aka counter pick tier)
Freeze Mage
Grim Patron Warrior
Tempo Mage
Renolock
Aggro Shaman
Anyfin Paladin
Oil Rogue
Tier 3
Hunter, Control Priest, Paladin decks and whatever else that is usable.
Tier 4
Nobody cares