and who mentioned premades?
If you read my post, you'd see that I allude to premades because a DPS cannot demonstrate his full potential unless he is confident that he is being healed. This doesn't necessarily occur only in premades, but a pocket healer generally comes with skype and/or other means of coordination.
As to why I was mentioning DPS numbers in a thread about total damage and total healing, I was referencing Goesid's post regarding which classes have the highest damage and which are similar.
I feel that, unlike your own post, was a contribution to this thread.
Here's another contribution:
Restoration Druids are realistically the only healer that can mitigate hunter / rogue damage while still maintaining high heal numbers, making them the top "healer" in the bracket, in my opinion.
Holy Paladins have the highest heal numbers, and Lay on Hands does a lot more than any other healer's OSB (Oh Shit Button). They have awesome consistent mobility and decent instant cast healing to back that up. They also have magic/poison dispels, allowing FC's to do battlegrounds without a pvp trinket. And of course, Hand of Justice can be the difference between winning a teamfight or losing the game, capping a flag or having the EFC cap a flag.
Restoration Shamans are unique in the number of mechanics necessary to play RSham competently. I would say that they are probably the highest healer skill cap. Their "wall" is also perhaps the strongest out of any other healer (perhaps excluding the Divine Shield of Holy paladins), and they benefit from stamina at an extremely high rate. Whereas Rdruid's Bear Form shuts down its healing and Divine Shield is a long cooldown, Nature's Guardian + Mark of Tyranny + Battle Standard + Ancestral Fortitude can easily get an appropriately geared Rsham to a monstrous 3500 health. The mechanics they have available to them make up in some ways for the lack of "strong" healing but not entirely.
Discipline Priests have strong reaction-time based healing. While Rdruids have Rejuve-Swiftmend and Hpallys have Holy Shock (and/or Lay on Hands), Disc Priests have the more consistent PW:S + Penance combo. Their CC is unmatched as a healer, and their damage is on par with even Holy Paladins. However, the cloth armor type coupled with no actual movement-based defensive cooldown (No increased movement speed) equates to essentially dying solo to a hunter when conc shot is applied.
Holy Priests are honestly more of a DPS than a healer, in terms of comparison to Discipline Priests. However, they are more about controlling enemies than burst damage/healing, which can be more beneficial in some potential scenarios.