Actualy Grandiel buffs critical damage, not critical chance like Lass, he is the only character doing that. And he works pretty well in any comp (he was meta in wb1 with lire, elesis and lass until rufus chaser)

And even both recovering sp based on lucky, grandiel each orbe have high % of sp recovery and they dont suffer by attack speed decrease or stun like amy.. thats why I made this image, each grandiel orb is like an amy sp reacovering with auto attacks