In terms whether it works in practice, it already has. As for how it impacts the overall raid DPS, it's something that can always be balanced and accommodated for (and was previously accommodated for) Heck, as one person put it in the healer forums: I'd rather have Miasma at 35 potency and a Biolysis at 35 potency than a just a Biolysis at 70 potency.
With regards to healers who only like to deal damage - or seem like they do, I find these are a minority and don't think the healing community as a whole should be punished for the actions of the few. I say "seem" because I don't think this is something you can tell unless they explicitly say it, because what seems like a healer who only wants to do damage could just have a poor healing/DPS balance. And if there are people who are really like that, I've yet to come across one in my 7 years of playing. I expect I might assume it if I see a healer not ever case a healing spell. But yes, I have seen healers who maybe DPS too much at the compromise of their party.
We also have tanks and DPS who don't do their jobs properly and cause wipes. But I don't think is just refusing to do their job, there's people of all experiences and people make mistakes. I've mistakenly let people die, this isn't because I've been too DPS focused or because of anything complex, it's just misjudgment on whether I should heal or not. You might find that tanks aren't using their cool downs, so you have to adjust for that, you might find that tanks are in poor guy and have to adjust for that, or people have eaten avoidable AoE's and you have to adjust for that. They're all things you can misjudge (just as people can misjudge said AoEs, or pull the number of mobs they pull misjudging the healer's ability).
The thing is, this is no less a problem today than it was in ARR, HW or SB. As I covered in a previous post, maybe DPS complexity isn't the issue here. It's about focus and prioritizing heals at the end of the day, if you're focused on DPS, it doesn't matter if you're casting Broil over and over again or whether you're casting Miasma -> Bio -> Bio II -> Shadowflare -> Broil. The requirement is that you don't cast your next DPS spell and instead cast a healing one.
By contrast. It seems very common when I get Titania in a roulette that the DPS's of the group fail the DPS check. This is because they're either not doing enough DPS or because they're not dodging AoE's. Dead DPS means not meeting a DPS check, so these situations can be make or break on the success of a run. This is because the requirement is for the DPS to simultaneously maximize their DPS and dodge.
There are tanks who poorly position the boss or go as far as facing them to the party and cleaving them. Many cleaves are tank busters that'd kill many healers or DPS. Like Shiva's, I've have had a few lately where tanks have done this and killed both healers.
I just don't think we should make the game easier because of inexperienced players, bad players or players who refuse to fulfill their role properly. My general view here is, if people find parts of the game inaccessible, it's better to offer tools to help them learn rather than to dumb things down. Because we start thinking about how we can patch people's mistakes, we're going to start making things mindless.
And it's something I've praised the game for in its design, if you look over A Realm Reborn dungeon design and trial design, you'll notice there is a gradual progression of difficulty and the occasional skill check. It aided how people learned. Taking something like Satasha, the first dungeon, it's very forgiving if you tank or healer messes up. Anybody can tank the damage in Satasha. Heck, once, I was dumb and forgot to repair my gear as a healer and it broke...we still made it.
One suggestion I have had before is "Training Logs", something in addition to the Hall of the Novice, something that may teach you a certain principle and gives you a dungeon that suitable for practicing it in.
And to be fair, out of all the ways you can "fix" healers, arguably the DPS option is the most beginner friendly one. Because inexperienced healers don't /have/ to DPS until Savage really and some EX fights. Sure it /helps/ but the game is lenient on DPS checks enough to not be an issue Heck, you can watch my Titan EX clear on YouTube, I committed the cardinal sin of doing 0 DPS, because I was more focused on learning the and remembering the fight. Subsequent runs I did throw in DPS.
But it means we can keep the healing difficulty exactly as is. Even if more DPS moves means reducing some of the healing bloat if they needed to compensate, they can boost potencies of heals or/and reduce recasts.