You honestly need to learn the role... I personally as a dps and healer pull mobs in lower dungeons to see how the tank handles agro... If they can get it back from me I know they know what there doing and say nothing... If they don't get it back from me I educate them on what needs to be done... Ask your dps if they can pull the mobs cause you want to test your skills... This game and its jobs are learning experiences only... As long as you can hold agro thats 95% of your job the other 5% is dodging aoe's and knowing where to tank the enemy at, which can easily be achieved by telling a group your a new tank to the trial/dungeon... Most people will help you out...