I love threads like these, it really brings out people that know how the game works vs those who will defend misguided feelycrafting until they're blue in the face. Healing has worked the same in this game since the game started regardless of how you feel about it, though this doesn't just apply to healers either.
No matter how a role functioned in another game you've played it does not matter whatsoever in this game. The OP is basically spot on with the overuse of heals and this strange "everyone must be topped off" mentality that has come from other games (FFXI is actually a different game by the way) only hurts your mp pool and your team's damage output/healing synergy.
I think there's a key thing that most people forget and that's bosses are also bound by the same GCD we are. There won't be a string of attacks that goes out before you have the chance to heal. If you look at the timeline for any bosses moves they're always spaced at least 3 seconds apart. If you know the fight and don't stand there wondering if you should heal for 10 seconds you will almost never be caught off guard because people aren't 100% hp all the time.
Yes, you should not keep people topped off 100% of the time when regen ticks will get them to 100%, especially when no damage is coming out that will require them to be topped off before regen will do it for you. That's just a waste of mp and needless overhealing no matter how you feel about it. If you truly feel that people need to be 100% health all the time that means you should focus more on learning the fights and when people actually do need to be topped off. HoTs are flat out the most efficient form of healing no matter how much you aren't comfortable with that fact.
As for your last point, there's no need to blindly go by anything. There's tons of examples and data to back up most claims that are essentially common knowledge by now. Just because it goes against your feelycrafting doesn't make it wrong and being open to advice and input from others is key to improving as a player. People who plug their ears and pretend to think they know best are often the subjects of the tales from duty finder stories..