I wouldn't class these as "stupid", but things that could have been adjusted.
I don't think it was necessary for Erzi to be a main character. If you don't kill Dax you have to have it return, but I think they could have had an episode or two with a guest character and deal with the whole Dax is back stuff and get it out of the way. There is a gender imbalance, but the show had some strong female supporting characters who could have been given more prominence to help address that.
The seemingly forgotten point of Starfleet in the Bajor system was to get Bajor into the Federation. Would have liked to see/hear something regarding that towards the end. Best case, see Bajor join the Federation.
MU Vic...a step too far in an episode that was probably one too many visits to the MU.
Weyoun's comment Breen is a pleasant place. For some reason it made me roll my eyes when I heard it. The Breen are mysterious, we get it! Plus they seem terribly careless with their refrigeration suits. People were constantly stealing and wearing them.