Tanks are at their most fun when you can solo certain old Extremes and Savage Raids

[Deceptus]

In the same way, healers should not be able to mitigate (ie. we should not have barrier healers, that's literally the job of tanks to protect the party). But we do. Tanks and healers have always been stepping on each other's toes and that has only grown.

Preventing damage is literally the same thing as healing. . . otherwise healer shielding wouldn't exist.

It's a concept called "effective hit points".