Folks, as I stated before, DAI is ultimately a game and not a book. With that being understood, even with this being BioWare, they will never let lore, story, or any other reason cause a detriment to the fun and experience of the game itself. Dedicated healing, for all intents and purposes, is bad for variety, flexibility, and is an unoriginal and stringent crutch to lean on. Much like in an MMORPG, the entire "purpose" an a healer is to keep the rest of the party alive because of their own role limitations. This is why the holy trinity in a lot of ways is a terrible and antiquated system by today's standards.
The entire philosophy of being dependent entirely on a healer to survive an encounter is a limitation and a narrow approach to role playing itself. By eradicating this unnecessary limit, we are now much more open to play with more variety and options in the roles and classes we choose. It leads to a scenario where we have to be more aware of our health pools and can't depend on a dedicated healer to resolve every dispute. This provides challenge, customization, new tactical opportunities, and allows other roles to be more fleshed out without needlessly being underpowered to legitimize a healer.
The only individual who should really be upset are those who generally prefer to be a dedicated healer. If you don't like to tank or deal damage, your role has been largely removed. That being said, there are still plenty of support abilities and opportunities that will be vital to a party's survival. You just won't be leaning entirely on health bars to survive an encounter now. It's unfortunate for fans of healing, but overall this is an amazing gameplay move on BioWare's part. It will only make the combat that much more impactful and memorable.