I feel that mixing up role and identity.
Shaman from WoW is a decent example. If you were to describe its identity how would you do so ? You certainly would not say "raid healer" would you ? That just its role as a healer. All it skills and ability were incredibly unique and fit into the theme of Shaman. They were this really cool supportive healer with neat chain heal mechanics and creative and neat ways to heal main tank.
WHM role certainly is a aoe healer but when you start asking what is its identity ? What theme are all its skills based around you sort of end up with nothing and just end up repeating itself [It gots gud heals]. Here the thing having good heals is not a identity, on the opposite its a requirement for all healers. To preserve that pseudo-identity you would have to do what you wished against and water down ever other healer. Which is exactly what SE tried to do with AST. They made heals weak because it crossed over WHM's [I heal gud] identity.
WHM is in middle of a identity crisis with nothing to call it own with little to no theme. Unfortunately its not something a patch can fix. Most likely it be this way until 4.0
