I don't mind the dragons being sent back without being defeated because I feel it was an intentional plot point, with Mavis commenting that none of them could defeat a dragon, and all the DSs not being satisfied with their performances. I feel like that'll lead to some development later for the DSs
However, if the author was going to have the dragons appear and do battle with the slayers at all, I'd have liked to see more of it before they left. Besides Natsu versus Motherglare, none of the other fights were really shown. I'd have really liked to see more of those
Dance Tournament sounds weird for the next chapter, but I won't be surprised if it's exactly what it sounds like. The two chapters after that though, can't really guess.