Make it so you can't join a fight, if there are no opponents within your level range, meaning a level 19 can't join if there isn't at least a 16, or an 11 join if there isn't a level 8 or higher.
It'll make the fights a bit more realistic, and fun, and won't harm anyone except for the leechers and people who didn't deserve to win, but still won because someone who can't die comes and joins last second.
Problem exists on both sides, and I've been a bit guilty in the past too, where I'd join a fight about to become a GB but no other mages or even a levle 11 in fight, but it's still not fair to those trying to get valor/scalp/exe and have fun, if someone who gains NOTHING from the fight except to make the other side lose, joins.
Just my thoughts.
Examples can be seen most recently here:
http://warofdragons.com/fight_info.php?f…80&server_id=10
and here
http://warofdragons.com/fight_info.php?f…02&server_id=10