The best defensive pivot for you would probably be Tangrowth, as Tangrowth has good stats and regenerator, and Tangrowth can switch into attacks that threaten some of your other Pokemon. Also, Electivire is pretty badly outclassed by Tapu Koko. Replace Charizard's dragon pulse with roost for healing, and give it timid nature to outspeed more stuff. Replace Greninja's grass knot, surf, and dark pulse with gunk shot to resist grass and fairy, spikes to resist electric and lay hazards, and u-turn to ease predicting switches. Give it 252 Atk/4 SpA 252 Spe naive to power up gunk shot and u-turn. Make sure it's male and not shiny, or opponents will easily be able to tell that it's not battle bond. Replace Garchomp's poison jab, stone edge, and dragon rush with swords dance to boost physical attack, outrage for better accuracy, and stealth rock to lay hazards. Give it a dragonium z to power up outrage and jolly nature to outspeed more stuff. Replace Tyranitar's thunder punch with pursuit to more certainly hit dark-weak opponents. Give it a choice band to power up its attacks and 252 Atk/4 SpD/252 Spe adamant to outspeed walls.