I guess my concern is that the pure/shield distinction is meant to be a distinction in result, or in what is uniquely provided, but what you're aiming to replace it with is only necessarily distinction in process.
For instance, a barrier healer theoretically provides {not dying from one-shot heal checks or to a further degree of vulnerability stacks} and a pure healer provides {not dying from repeated heavy damage}, but what does "heal via damage dealt" actually provide?
Healing through damage dealt is, in itself, only a constraint, so what's the reasonable compensation? Would it, as per examples from other MMOs, just be "slightly higher combined damage and healing if/when everything's going right"? Or would it simply be some other utility feature of the job that has nothing necessarily to do with that constraint anyways?
I don't feel like the present failings in how (un)equally attractive different jobs are for raiding are even because of that Pure/Barrier distinction, though. It's more a matter of their just not being enough (especially, GCD) healing to do for something like WHM to present any advantage outside of its single arbitrary bonus -- Afflatus Misery for multi-target burst.
I've heard the same, but... it doesn't really make any more sense than the idea that Pure Healers should be able to meet every mitigation check.I've heard it said that the Pure/Barrier dichotomy doesn't work because Barrier Healers have to be able to heal (non-coordinated group content) even if there are 2x Barrier Healers. This ultimately makes Pure Healers redundant.
If either one brings something wholly unnecessary, they start to seem redundant, but, perhaps worse, if both are required then you have a very high chance of "Death by composition check," which would ruin any matchmade content unless it badly worsened an already bottlenecking queue by truly splitting it into those sub-roles.
Personally, I feel like the distinction, if it's to be drawn up roughly as it already is now, should simply come down to different particulars of ease. Pure Healers should be better able to salvage stepping in fire when you step in the fire. Barrier healers should be better able to keep you from dying (to unavoidable damage) because of having stepped in the fire almost a minute ago (via vuln stacks) and occasionally sacrifice their own would-be damage for others' uptime.