1) You need your AW Iris to be healing BOTH your tanks as I've heard AW healers reduce the duration of the Dracolich's paralyze effect by 50%. Atm, your Iris is only healing Bernice and not Raichi. If you're not confident on switching both healers positions, maybe try AWing Chydis and raise her to AW50.

2) Try using a third unit with dodge like rogues, monks, foxes as your back-up if the Dracolich escapes both tanks. Lock the Dracolich a second time with said unit in the slow beside Bernice. If this happens, you can freely activate Raichi's skill as she is no longer a target for the Dracolich's paralyze.

3) You could retreat your Niel and Alissa to deploy your Rosel or a archer at the slot beside the left healer. Miruno can be placed in the bottom corner of the map. This is just to speed up the process.