You see, the problem with SE' way of thinking is, they're not looking at healers for the amount of damage or support they can do. They look at how well they can heal.

This was made obvious back before 3.0 raids, where Yoshi told us how everything was Balanced to not require healer DPS at all.

If you look at healing alone, WHM is indeed viable. As long as it can fulfill it's role of keeping people alive, it's good enough to SE. It's a really faulty way to look at balance if you ask me.