Spirit of the Dead doesn't seem to fit, Holy Nova is way worse than most of the excellent massive removal Priest has, you probably don't need a full playset of both Pain and Death, and yeah you'll definitely want more draw
C'thun decks have a very low winrate (good luck trying to get to legend with them), but they are indeed decent decks to use if it is your first time pushing wild.
https://www.hearthpwn.com/decks/1217890-cthun-rubmles
Here's my current deck I'm no pro, but it feels like I need more draw, possibly taunt. Any tips appreciated
Spirit of the Dead doesn't seem to fit, Holy Nova is way worse than most of the excellent massive removal Priest has, you probably don't need a full playset of both Pain and Death, and yeah you'll definitely want more draw
Spirit works awesome, maybe down to one? I get lots of added value if I can keep it a turn or to
C'thun decks have a very low winrate (good luck trying to get to legend with them), but they are indeed decent decks to use if it is your first time pushing wild.
I think your deck needs more board clears like Excavated Evil and/or Mass Hysteria instead of Holy Nova. Also, it's good to include Shadow Visions, Entomb, and one more Twilight Darkmender.
If you have the dust, adding Shadowreaper Anduin, Lyra the Sunshard, Justicar Trueheart, and Ragnaros the Firelord (or The Lich King) will boost your winrate by a lot.