For low level duties the balance of a raise is fine. For late game duties there are several issues. And those issues are basicly:
- If the team has no other job that can raise, its always the healer. In this case, you generaly want to protect the healer for balance (making things too easy)
- If the team has a job that can raise, it does allow the healer to occasionaly die. This allows a lot more damage to be dealt as there is a fallback.
- The tank already has such fallback (the healer). But the other way around generaly doesnt exist. Tanks are on that more graceful.

The more methods you have to raise a healer, the more you can scale up the damage since it becomes less of an issue. But you dont want this difficulty at low levels.