If the dungeon quest was seperated into two ways, like individual and group, it would have been better in my opinion, as most of the players already mentioned about timing problems. For example, if the reward of group dungeon is light stone (If completed in 1st try), it should take 3 times for the people who have been doing dungeon without group to get light stone.
Doing so, will even balance the reward system.
I like the Santa and Zekrom quest, they were ezz and worthful to do as their rewards were satisfying too. At last, I really appreciate the hardwork put in by the PRO staff team. We expect even better quests from you. So, gooood luck!