AITA for leaving a group because they refused to let me do the quest?

I'm a healer.

Was in a dungeon. DLC one. I asked to do the quest. They said no. Had too little time to do it .

So, about halfway through, I left the dungeon.

I then started to get a ton of insulting messages that me leaving caused their tank to leave, and now they have to wait or skip their daily today.

I don't think I was an arsehole, cos I queued specifically for that dungeon to do the quest.

I'm free to leave whenever I want. If they had let me do the quest, it would have saved them time

What do you think fellas?