Does Pianus even spawn anymore?

At least thats how i see it. The only way to get a Pianus is to be the first one in the cave after a SC or take time of the SC and check every 8 or 12 hrs (IIRC thats the spawn time of each pianus after they are killed)

It's a misconception that server checks reset boss spawns.

The only effect they have is, if the boss would have respawned during the server check then it spawns immediately when someone enters the map.

Timed spawns happen if
1) Enough time has elapsed since last time they spawned (for pianus, 24/36 hr)
2) Someone is in the map
3) There are fewer than max # mobs in the map already.

Most bosses have reasonable respawn times so a 10 hour server check clears them to spawn again. Pianus doesn't.