Who in the world bails on Haukke Manor of all things because there's a new player? Especially if it's a DPS -- they could be AFK the whole dungeon and it literally would not matter. I'm glad you stuck around and the dungeon ended up finished, though. Hope the healer enjoyed their penalty.
To contribute with my own story: I queue up with three friends (myself as a BRD with a DRG, WHM, and DRK) for the trial roulette. Thornmarch: Hard. Easy peasy. Go through the normal motions of annihilating the Moogles in the first phase, the Good King gets spawned, go about my business killing the BLMog when suddenly, we wipe. I can't recall ever wiping before to a roomwide ultimate like that, so I am confused (as are the three friends I'm on Discord with). I really don't remember what makes that wipe happen -- I'm still not sure honestly -- but I suggest that maybe it has something to do with the two tank Moogles not being tanked away from the king.
Attempt two, my internet cuts out as soon as we pull. I reconnect shortly and manage to get back in just in time to kill the BRD Moogle before the Good King is summoned again. For some reason, the PLD (who hasn't been moving up to this point, at least since I got back) types "wipe?" in the party chat. We obviously do not wipe to the phase transition. DRK friend picks up the tank Moogles, we DPS go about our business of blowing things up... and the PLD just stands there. DRK asks them to pick up the King. PLD stands there. So now our WHM friend is tanking the main boss while the rest of us clean up the Moogles and the second WHM handles the bulk of the other healing that needs to be done. Things continue this way until Good King Moggle Mog XII is dead. It would figure that we get an AFK tank on one of the few trials that our DRG friend (who hasn't quite reached Heavensward) has unlocked that actually benefits from having two tanks... The kicker was that we noticed the crown next to the PLD's name on the way out.
TL;DR: AFK mentor PLD on Thornmarch: Hard helps to prove that WHM is secretly a tank job. Once again, not really a horror story, but more of an eye-roller.