The only alternative I see to removing the rewards entirely is a combination of two things:

1) Have the queue available only during certain time windows. Example: on NA servers, you can only queue during 5pm EST > 1am EST. This would take out the factor of win traders doing their "work" during the wee hours of the night and morning. You might say that some people who work off hours may have trouble participating, but guess what? The queue doesn't pop during off hours anyone which is what allows people to win trade.

2) Make a system in which you need to register a team, like is in place for Palace of the Dead. This way the exploit mentioned in the OP would be null and void, totally fixed.