One suggestion-once you join in a duel, you cannot leave unless you A.) are defeated or A.) win the duel. Too many times I've been at the end of a duel, to have another player join in at the last second only to flee as another creature joins in. Very frustrating when you are low on points, cards or mana.
It would be better if there was a way to seal a battle so random bystanders can't just jump in. Like after the third round they need permission of one of the fighters to join.