If I am forming the group to WOW TBC Gold acquire a certain item, and I have already put the tank/healer together what is the reason I would want to face a competitor DPS? The item must be dropped and I must play a coin toss game in order to obtain it. DPS are a dime a dozen.

If they're front, I don't mind. I managed my own SP group 11 days consecutively to allow the trinket dropped and made sure that each time the other two dps wouldn't need it. Many of them wanted leather legs or just to switch their attune. It's a bad idea to let them tell you, or worse, at the boss. In the end, they'll add insult to cheap WOW Classic TBC Gold injury when they let their friends roll on it and trade the attune with them.