>>528690793
Kitty is just, fine. Where portal flips the balance on it's head is higher up.
Just look at Sylvia, a 6cost 5/5 that unconditionally deletes 2 enemies while drawing you 2 cards or healing you for 4. Leaving you with a 8/8 rush immune. All while not requiring any setup at all.

There's literally no reason for this card to provide so much value at no cost, even if it were legendary. It's good against anything at any point in the game.
Sylvia is better than 80% of legendaries in the game.