The far east and west sides of the library are safe spots for camping this named. Stay just slightly down or all the way down the ramp and you're fine.
There are two roaming spawns in the library. Either of these are placeholders for the named. The room just south of the library has five stationary placeholders for the named.
The placeholders are noticeable after a period of time. They always spawn, eventually, as either convergence (of tide and wave) or construct (of surf or water). They also spawn as defenders, oracles and watermancers but never as experimentals.
So far as I could tell, there are no stationary PHs in the library and no roaming PHs in the room to the south of the library.
Non-summon mobs:
Defenders, construct of water, construct of surf, experimental champions. The construct of surf usually stands his ground and nukes.
Summon mobs:
Oracles, watermancers, arcanists, convergence of wave, convergence of tide, experimental arcanist and experimental overseer.