yeah thing is waterfall pretty much does that much damage without having to take up an entire moveslot :/Earthquake should be a slash on the Dragon Dance set. After one DD, it outspeeds Raikou and Megaman, and OHKOs with Earthquake.
+1 252 Atk Life Orb Feraligatr Earthquake vs. 32 HP / 0 Def Raikou: 465-549 (141.3 - 166.8%) -- guaranteed OHKO
252 Atk Life Orb Feraligatr Earthquake vs. 0 HP / 4 Def Mega Manectric: 294-346 (104.6 - 123.1%) -- guaranteed OHKO
252 Atk Life Orb Sheer Force Feraligatr Waterfall vs. 0 HP / 4 Def Mega Manectric: 230-270 (81.8 - 96%) -- 62.5% chance to OHKO after Stealth Rock
+1 252 Atk Life Orb Sheer Force Feraligatr Waterfall vs. 32 HP / 0 Def Raikou: 363-426 (110.3 - 129.4%) -- guaranteed OHKO