I don't think there is anyone at level 70 that can tank a Manifestation, regardless of level or class, their special attacks do 3k to 4k easily. I have 6k health and the only way I can kill one safely is with hit and run.

Humans are good for very high level guardians, or Lucidian. If you're Celestine you care less about the int unless you want to bash, so might choose Loboshi.

Mugwump Nihilist. Need I say more.

They throw hexes so fast its scary.

just go dracnari and be done with it, good int good con good fire resistance.

go live on sagi for a while. That being said you could also go loboshi, or taurian.