About Branch job in FFXIV and Specialization in WoW

Many people think create new branch jobs like SMN/SCH are hard to balance it. But I think branch job concepts similar to Specialization in WoW before WoD. Some spec have different role and must use different gear set. Each class have core abilities that resemble to class actions and spec abilities resemble to job actions in FFXIV. The big different is WoW have a lot of passive (same as traits in ffxiv) to make different between spec. Moreover, some abilities and talents can give different effect or changing skill mechanic when change spec too. I think it is still possible for making branch job in future. WoW can balance it for long time, then why would FF can't do it. What do you think about this?