Hardest raid encounter on this server?

[nyclin]

Sontalak or Tunare by far. Sontalak is just a beast, and one instance of low HP aggro can wipe your entire raid.

Tunare herself isn't *incredibly* hard though there is somewhat of an element of RNG to her fight. The real difficulty is what Cucumbers said - keeping people engaged after 6+hrs of clearing PoG.