User blog comment:Koishi-Komeiji/Nagisa Momoe/@comment-32751919-20190824093216/@comment-24965192-20190824094024

Her NP gain is only good when you use her Arts cards, and yes the Arts up skill is solely for NP gen and more damage from Arts cards. Her NP by itself is extremely powerful, so it wouldn't have been wise to give her enough NP gain that she could loop her NP. But if she were in an Arts team, she might be able to pull that off.

No, there are no Servants with the Cheese trait, but you could always find a Medb and apply the debuff on her. Yes, the trait change works the same way as Paris, but the only difference is that Nagisa's is more RNG the more enemies there are in the field. In a battle against three enemies, there is 33% that the debuff will hit on who you want it to hit. However, if it's against a single enemy, then it's a 100% chance. Take care that the debuff will still miss if the enemy has Magic Resistance.