I was looking through Irisviel's page, and it says her NP gain rate per attack is 0.59%. This is lower than Heracles, and his charging seems extremely low to me. Is there something I'm missing?
Buster cards don't fill np bar on hit, making Hercs QABBB deck very weak in np generation. Iri has 3 arts cards, and even with that low np gen per hit, she will fill her np bar way faster than Herc, especially with instant 20%s from arts chains
There are a few other differences as well.
The NP charge rate is per hit, not per attack. All of Irisviel's attacks have more hits than Heracles's. (She has 3 hit Arts cards)
Like most Casters, Irisviel has Territory Creation which boosts her Arts performance. With 3 Arts cards in her deck, that helps a lot with NP charge.
Lastly, her second skill boosts her NP generation by 20 to 30%.
According to Cirnopedia, she only gets 0.42% gain per hits and usually Casters have Territory Creation Passive to boost their art cards. Iri has B rank of that passive (8% boost), so it would end up around 0.45% per hits with 3 hit counts (1.35%) which is kinda low for casters standard, so you may want to give her CE like Divine Banquet or Prisma Cosmos. But, if you can consistently doing arts chain, that won't be a big problem.
It's not "per attack" it's "per hit" so if the move hits 3 times she wil gain 3x as much. Not to mention she has 3 arts cards (which innately give more NP and can form arts chains) and a passive that boosts arts cards meaning even more NP gain than that.
