This is the sort of experience you get in some novice networks as well. I remember many occasions where a new player asks a question (they are just starting Sastasha) and there's always that mentor that will explain a level 100 raid opener to them when they literally have 3 buttons at their level. So the information overwhelms them and they learn nothing.

There is also a prevalent mindset among a lot of players and mentors that they need to "teach" people how to play "correctly" in dungeons.

The reality is that a complete stranger "teaching" you things in a dungeon usually comes across as "blurting it out rudely" and is likely to be interpreted as an insult. People often go into dungeons with the assumption other players want to bite, so this first impression confirms their bias that you are rude and want to bite like they assumed.

It's also not necessary to play perfectly or optimally in a dungeon, and not really worth even trying to make that the case if it isn't. Some parties will melt bosses and some won't and that's the beauty of a dungeon.

The people who try to teach everything in a dungeon often don't see the forest through the trees. A lot of sprouts are actually in FCs, discords or novice networks and are actively asking questions about the game to people they actually know and trust. Thus they will learn these things eventually if they desire to.

What you described seems like it may potentially be reportable, by the way. They often action people who are rude or badger you like this.

As regards the specific scenario, you usually don't need many if any heals in an expert roulette due to an overly generous ilvl sync but may depend on the tank and their gear. As the memes go, a Warrior or Paladin can do a giant pull in expert without a healer at all and survive it, or flat out heal their party if the healer dies during a boss fight. Because of this you can settle for pure ability heals between attacks in expert unless something goes extreme wrong involving double digit HP, deaths, vulns, DoTs, etc. I'm pretty sure a healer wasn't healing me the other day in the latest expert dungeon and had to use my CDs well to cope in some parts, but healers got free abilities that don't impact damage like Whispering Dawn, Aetherpact, Fey Blessing, Seraph or Aetherflow heals (may as well use these in AoE situations anyways).

But as I said, it does not matter in a dungeon and personally I just go through the dungeon as a Warrior regardless of if a healer is using lots of heals on me or not. No point badgering people about stuff. Should just let them have their fun, however they want to have it.