Typical Dark Teams

Here are the best element combos with dark I know of, roughly ordered by preference, with their best fusion skills. In most cases variants exist.

5/5		◲⧉	great fusion combo, full auto
4/5		◲⧉	good offense, sometimes used on moon gate
4/5		◲⧉	sometimes used on moon gate
3/5		◲⧉	sometimes used on moon gate
3/5		◲⧉	good against fire+light
3/5		◲⧉	also good against fire+light

All of those teams are only viable if you have two good totems. If you only have a good dark totem, better heal your team with Tidus. Maybe also replace Keros with Araji or Eden.