In DBO, what is considered a healer/support class? form looking at the skills, it seems only the namekian Dragon Clan has true healing abilities.

Heres the list of characters that are support/have supporting abilities

Dende Priests - they are the full healers in the game, and is the class that is more focused towards support then combat.

Poko Priests - Can heal, but they can only do the basic healing skills. They can summon monsters to aid by their side aswell.

Ultimate majins - You can either make one a full PVP character, full support or a mixture of both. Their main role is buffing players.

Grand majins - Can be support aswell, although you would be better off going Ultimate majin.

If you are going to go with a character with a supporting role, most people will either tell you to go dende priest or Ultimate majin, as they are the best supporting characters there is in the game as they have been proven to be the most useful.

as tempest said before get dende priest or ultimate ^^ even tough dende are most needed in any guild and for any dungeon runs^^