It is highly contested what seperates the good from the bad and the bad from the downright loathsome. Of course, most would say that bad is seperated by loathsome by player attitude. To that, I would be inclined to agree.
What I would like to offer is a few thoughts on the DPS classes. My main character is Straath Phalynxscale, an Iksar Guardian on Innothule. My job as a tank in a group is to set what I like to call a "hate threshold".
The job of every single DPS class is to do as much damage within that threshold. It is not the job of DPS classes to steal aggro away from the tank by mashing every skill button on your hotbar. In fact, the detriment you cause by doing so can be immense.
Firstly, scout classes 85% of your DPS comes from behind or flanking the mob. If you do damage outside of the "hate threshold" and the mob turns around to face you, your DPS just took a huge cut because you can not get behind the mob. Evade and stop attacking. Let the tank regain the aggro and reset that threshold, then you can go back to killing.
Mages, you have the damage mitigation of a wet paper bag. Manage your aggro!! All you gain by overnuking is, best case an exhausted healer wishing for more power or, worst case, Welcome to Dead, Population--YOU. If you get aggro, stop casting spells, period. Let the tank regain the aggro and reset that threshold, then you can go back to killing.
Admittedly, different tanks set different thresholds. Find out where that threshold is as quickly as possible and use it to your advantage.
The bottom line is that a chimp with A.D.D. can sit there smacking buttons. Your job is not that mindless. Let's see a little finesse from our wizards and swashbucklers. That is what seperates the bad from the good.