Does Pianus even spawn anymore?

Why?

I'm assuming this is back when Pianus was actually worthwhile to hunt for exp/drops.

Are you complaining about Pianus in GMS or JMS? For JMS, I catch Pianus fairly often actually. I've killed like 7 or 8 on my Kanna and only looked a few times. I think it completely depends on when you check. Next time I find one (I don't know when that will be), I'll let you know the time. I know I usually catch them around the same time, but I could be wrong.

As for GMS...no idea.

Also @ above debate on spawn times for Pianus: If this is JMS, it may be different. I hear Manon is a 1 hour spawn in GMS, but in JMS he's at least 6.

GMS Manon is most definitely around 6 hours. It's super hard to find one nowadays.