Interesting take on the list, but here are some thoughts.
Nimbus is too weak a card. It’s ok for midrange, but this isn’t a midrange deck. I’d swap it out for feral spirit. Let’s you draw more with your 2 mana spells, activate overload, and protect you/your minions so you go face.
Southsea is fine. It works as a 1 drop into earthen might, but I’ve found Wartbringer to be a more consistent “deal 2” effect. Also doesn’t die on dealing 2 to a minion.
Electra has stand out moments to win games, but it’s not worth running. It’s usually just a 3 mana burn spell. It requires another card and will often overload you more than you want. Second earth shock to deal with taunts and mechs is much better.
Dire wolf doesn’t fit this burn plan. It’s meant to snowball board control, but that becomes less important by turn 4-7. You want a better 2 drop that doesn’t require board to be good. One choice is the 2/3 murloc that adds murlocs to your hand whenever you play one. Good for a board flood vs warrior, but not much else. I prefer Spellzerker, a 2 mana 2/3 that has spell damage +2 when damaged. Often will give you 2-4 damage on your spells, and has given me a couple of lethal setups by zapping it myself.
If you’re wondering why you should listen to me, I’m currently at rank 75 legend by only refining and playing aggro overload shaman. Been doing this for the last 2 seasons. Check the leaderboard if you want proof, my battle tag is the same as my username
Hungry crab is leaving
I think the best way to think about the scheme is as a 0 mana sap that makes the minion cost zero. It’s weak as removal, but it enables huge tempo swings by allowing you to play your minion and nullifying a threat for no extra mana. Another thing to point out is that tempo priest is coming together. We have the 3/2 for 2 that turns your healing into damag and the 3/3 that summons 1/1s for every spell you cast. It’s coming together