Even better I think BLU and DNC for that matter should have been jobs that fit all 3 roles, which would solve a ton of issues and make Tanks, Healers and DD all happy.

Blu could do it through spell sets and dancer through stances, which would all be locked in duties. They are both the perfect job for a system like this since they are so incredibly versatile. No gear or stats would need to change, with dnc abilities could be shared and have different attributes depending on stance, so icons, animations and what not wouldn't need to be changed or made new. It would be like bringing 6 jobs out at once.