It looks like you'll still have trouble with Tapu Fini. Unless it's weakened you can only 2HKO it.
252 SpA Gengar Sludge Bomb vs. 244 HP / 0 SpD Tapu Fini: 126-150 (71.5 - 85.2%) -- guaranteed 2HKO
All my calcs said you can one-shot the rest of the tapus, gyarados, and almost garchomp. This...