I msut agree that Coralhelm was unarguably a must x4, while we had a deck that ran:
Lands
Vials
Merfolks
11
Mana-less Counterspells
For some months we've been able to spend all our mana on pumping him without a sweat, but now we'll have to replace MM for a mana spell, and that'll force us to keep mana open at the end of turn. Thus, making pumping considerably slower. Still, I believe him to be the best single merfolk winning an incredible amount of games by himself, and I'll keep 4 of him, but we'll have to pay with another mentality.
My idea to test to replace the MM spots would be with 2 Dismember (I kinda specially fear Lavamancer now, and Lackey will come back) and 2 Stifle (since we're gonna be a bit slower, why not slow the opponent and gain some unexpected tricks in the process?).
Would you guys consider
Gut Shot maindeckable? It kills Vendillion, Spellstutter, Lavamancer, Dryad, Hierarch, MofRunes, Lackey, Confidant, Elves, Scryb Sprite, Peacekeeper, etc, without tapping a single land nor losing lives. This would just be an idea to keep our deck as fast as possible, by freely killing the earliest threats on the board, slowing the opponent down or disrupting his game plan.
Although for only 1 mana more we have Dismember, which can take down a wider spectrum of the meta-game. Anyway I think that this little red dude could be Dismember 5-6 if need be.