Ok. So I decided to wait a day so this didn't turn into a QQ thread, but...
On my warrior tank, only had 30-40 mins (was waiting on a text about meeting times) before I was going out, decided to queue anyway for a random normal dungeon, pulled Halls of Origination. After Anhuur, mentioned I was short on time but had time for a few bosses, mentioned it again after Anraphet when I knew what I had time for. Healer starts qqing something shocking, "mm. yeah sure, every tanks like this I'm sick of it", all sorts of snarky rubbish. Asked a second time, want to start on Isiset or something and I'll nick off after that or go straight to Rajh, healer replies "ffs Rajh. sigh". Then we started arguing, did Rajh but I think he implied that I liked the company of gentlemen and it all got a bit silly.
Anyway. I figure tanks are short, and 4 bosses (including the end boss) at a very rapid rate (doing most of the DPS), no problems at all and I was polite enough about healer mana, CC all that jazz. Any queue is better than no queue, and if I step out halfway through you'll get the next available tank anyway. It's really not a big deal. The healer asked "why queue at all if you didn't have time?" and left, I thought the answer's obvious... I had time to do a couple of bosses, so I did.
Does it put a bee in your bonnet when someone leaves early? I dunno, just be grateful someone's polite about it and not some spacky mongoloid imo. It IS the dungeon finder after all.