Aren't buffs wiped usually only wiped once somewhere around when shield goes up? I had used buffs in the past on 5 star raids with decent success and I never tried to one-shot with them, just increase survivability or speed up damaging.
5 star and 7 star are kind of a different beast.
For one, 7 star raids are lvl 100, while 5 star raids are lvl 75. Their HP multiplier is also way higher.
The movesets of 7 star raids is also generally much stronger and purposely made to provide a hard challenge.
Charizard had a special interaction where it'd do the debuff clear pulse only once, but aside that, both buff clear and debuff clear tend to happen multiple times if the raid feels like it once the buffs go down. Though in case of Cinderace, generally a single buff clear would send the raid straight into oblivion since he'd just wipe the floor with +4 stabs or Acrobatics right after it.
It's also worth mentioning that so far we saw that both Charizard and Cinderace had a "turn 0 move" that would happen before anyone gets a single turn. Charizard would Overheat one person and then debuff clear, Cinderace would cast Bulk Up right away.
It's realistic to expect that so will Greninja. What? I have no clue.