Every time I turn in a mission there is a pause afterwards, I believe from a save occurring. When you are turning in 10 missions at once this is very noticeable and makes it take much longer than it should. Would it be possible to either remove the save after every turn in, or at least turn in all the missions at once and then save?
Could the calculation for rewards be more complex with warlord missions vs random treasure chests found in the dungeons? That could be another reason for the delay getting more noticeable as more missions are turned in at once.
It also could be the reason above contributing as well (saving 10x instead of once).