So here is the thing, I love tanking, probaly every MMO I have played I was a tank.
I understand its job, I know what to do to be effective. Of course the thing that is lacking is dungeon knowledge, what tactic is used on a certain boss.

The dungeons till level 30 were kinda easy, holding hate ain't hard, taking a beating is kinda my job and never had I any complaints about unable to be healed.

Yesterday I queue'd up for the level 35 (excuse me for forgetting its name), I always mention that it is my first run whenever it is, the reaction I got was kinda shocking, people (the whm & smn buddies) called me a slow noob and left before we engaged the first group (it took me 1.5s to mark the targets).

Okay, it happens, not everyone has the patience I guess, I just queue up again. After a minute the teams was filled and ready to go, I mentioned I was new so unfamiliar with tactics, the healer sigh'd and left, the new DPS said they didnt feel like explaining and left as well.