Yep, happened to me in Sastasha for roulette today. As soon as I get in, the other 3 party members are all in the opening cutscene. At least one of them was new, and explained it was his first group instance ever. Okay, so before we get started, I did a Ready Check. The two DPS said they were not ready. Naturally, the Healer takes this as permission to rush ahead and start pulling the first group of mobs himself. We're really off to a great start...
All through the dungeon, this healer is running ahead of the group, hopping up and down as if to say "WTF are you doing, I am here for a speed run!" If I don't keep up the pace he'd like, he runs ahead and grabs the next group of mobs.
Edit: I forgot to mention, while I was checking the note that said which color coral to click on in order to trigger the first boss, he was keeping up his impatient jumping routine on the path ahead. When we actually got to the first boss's room, just before I get the chance to click on the correct coral, he hits the wrong one and proceeds to get poisoned.
When we get to the big chamber that branches off into multiple rooms, I figure since I need the experience (both level-wise and tanking-wise), and we have new people, we could explore the optional rooms, maybe do a full clear. But when I turn towards one of those rooms, the healer has already run off by himself, straight into another group of mobs on the direct route. Thanks, guy.
He has Cleric Stance on the entire time, without exception. There are numerous occasions where I am close to death, and CS never comes off.
Just before the last boss, I take a moment to explain what to do. I begin: "Okay, so for this boss..." -- he interjects immediately -- "idk". IDK? As in, "I don't know?" The speed with which he says this makes it feel more like "I don't care," but whatever. But how does he not know how to handle this boss? He has been charging through this place the whole time, and he knew exactly where to go whenever there was a branch. He's even wearing a robe that I recognize from my healer, which I'm pretty sure only drops from a dungeon. It is clearly not the healer's first time here. Anyway, I explain to click the bubbles when they start to act up or else it spawns adds, and in we go.
Do they click the bubbles? No, of course not, so I reel them in as they come. Do I get healed at all? Ha ha ha ha, no. Does the healer have the good sense to break out of Cleric Stance, even for a second? No. So, I die. The other DPS die. I watch him try to drag the fight out as long as he can, just standing there healing himself, still in Cleric Stance. I tell him he is in Cleric Stance. He doesn't respond, other than to say "Sorry I got distracted." Lovely.
We respawn back at the start, and I watch him re-apply Cleric Stance as soon as he possibly can. We did manage to beat the boss on the second attempt, but... jeez. I probably could/should have said something to this guy earlier, but I just got a vibe from him that he would not even care. The thought of just letting him die whenever he pulled had occurred to me, but I didn't want the rest of the group paying for it so I ended up swallowing my pride and just getting it done. Whoever you are, though, healer... you are a real jackass.