That's less to do with the NP interlude boosting the damage and more how Quick NPs are generally stronger than their Arts and Buster counterparts at the same NP level.
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And yet, 1200% -> 1600% is the same relative increase as 900% -> 1200%, or 600% -> 800% (if only they'd fix Rama's scaling so I wouldn't be worried about Buster NP being needlessly weaker compared to the other card types post NP interlude).