Hi there, welcome to the forum.
This fight is annoying for a few reasons:
1) Griffin starts off with stealing your buffs, then the very next turn he'll take his debuffs and throw them on you, which makes timing everything very important. Sometimes it can be nice to throw down a block debuffs if we have it available, after the buff strip turn. That will then protect us from any random debuffs we might throw on between those turns.
2) we can't control him with turn meter effects (but decrease speed is fine) due to one of his passives
3) the clock we're on due to the Celestial Bond passive ramping up the damage
So, we need to time things, and well.
It's early days for us still with our roster, so I think I'd go with Tomb Lord (though the A3 might be an issue due to Griffin passive), Ronda, Artak, Scyl and I think either Rector or Stag. Tomb Lord already does a bunch of what Stag does (dec attack/defense and speed down A1) but you can try to double up on having all of those available to get around Griffin removing its debuffs.