The following are videos of fighting the sortie basement bosses using the suggestions from the dev team. Party composition is 2 dd cor/sch brd/sch rdm whm. The strategy is in the descriptions of the videos. Using these strategies lets you use any dd you want.

Aita https://youtu.be/tKBOmzbm_Rc

Gartell https://youtu.be/m8Xg4rSrpYM

Triboulex https://youtu.be/D_PqlEtpcEA

Dhartok https://youtu.be/yqXOVfjyoDw

Example of what happens when you drop Aita's wings https://youtu.be/p-0Dv6PQHng