Crazy very unlikely theory, 5.15 is a "beta" for an omni role Blu, the skills we learn will more clearly define a "Tank" Blu, "Healer" Blue ect through stance skills and more skills specialised to those roles, by doing this they get data on how the Job performs at these roles in sync'd teams in a "safe" environment where the dont effect other roles and game balanc, so they can be further tweaked by the time theyre up to 70, then in 6.0 they role out at 70 starting level, with the ability to do multiple roles depending on which spec you pick.

Or I'm just mad and desperate but oh well speculating is fun