You could probably blitz it with all dark or valkyrie healer squads. The bosses (3 dragon knights) only have 130k HP each and hit for 4300 each. Valkyrie with two echidna, two sirens (or one and lilith), and a valkyrie friend should stomp pretty hard. Might need to pop echidna skills on masks and bosses. Your dark team looks pretty strong, too, with maybe a vamp or loki friend. Just get as much HP as you can manage to tank some hits.
If you really want to go safe, put your Siren as your leader and grab an earth ripper friend. Super easy, just takes a little longer. More HP and ATK you can mash in there, the better. Ripper/mech dragons preferred to speed up rounds and mow down the bosses.