Cube -> Echo -> Cube -> Ethereal Shift -> Ult/Refresher -> Repeat
You should focus on timing cubes to block enemy abilities, especially hard stuns and silences
Only use cube for general healing when you know you wont need it for ability blocking
Try to keep track of allied ults that cube is bad for
For example, always let Yamato or Giest ult to save themselves before you cube-save them.