It really just depends on the opportunity cost of healing. Mobs don't hit hard enough for you to be afraid. If someone dies, you can raise with impunity. There's no real resource management or time costs associated with healing. Given that sort of design, then yes, you should be predominantly doing damage because there's nothing else of value to do. SE is scared to let you actually heal, because feelings will be hurt if people die. So you dps.

But they also don't want to let you differentiate between healers on the basis of damage. There's a fairly big gap now between true DPS and other roles, because feelings will be hurt if you do more damage than the actual DPS. You're also going to tend to do very similar dps to other jobs in the same role. So how do you make the jobs feel different?

The only way left to differentiate healers is through resource management. If you want WHM to be a damage focused healer, then make them into a healer that regenerates MP based off doing damage. Let access to your oGCD heals be MP-gated, not time gated. What if, say, you had an on demand Tetra with a large MP cost where the only real limitation was whether you refreshed your MP back by doing enough damage? Recast times are not the only way to gate access to oGCDs.