Yes, these cards have to be from their respective wild sets, not core.
Here’s a functional at this juncture deck code:
Click to expand
### Nathria Secret
# Class: Shaman
# Format: Wild
#
# 1x (0) Murloc Tinyfin
# 2x (1) Dredger Staff
# 2x (1) Muck Pools
# 1x (2) Acidic Swamp Ooze
# 1x (2) Faerie Dragon
# 2x (2) Maze Guide
# 2x (3) Creepy Painting
# 1x (3) Humongous Razorleaf
# 2x (3) Tar Creeper
# 1x (3) Zola the Gorgon
# 2x (4) Crud Caretaker
# 1x (4) Lifedrinker
# 1x (4) Murlocula
# 2x (5) Muck Plumber
# 1x (5) Sinrunner
# 2x (6) Bog Beast
# 1x (6) Krag'wa, the Frog
# 1x (6) Mossy Horror
# 1x (7) Nozdormu the Eternal
# 2x (7) Red Herring
# 1x (9) Ysera the Dreamer
#
AAEBAZKrBAzhBIoHt2zFxwLD6gLL7ALv8QLBiQO2igT82wTL4gSg9AYJysMCqNkEtdkE9NwEs90EteIEpeQExe0Eyu0EAAA=
#
# To use this deck, copy it to your clipboard and create a new deck in Hearthstone
Oh, and for Sire’s sake, please use proper formatting, like I did above, wouldn’t you?