These are good, but you should retrieve Dialga's awesome move Roar of Time instead of Flamethrower as Game Beater said, it's not that great a stab.
That's all I can say, but how about items? A Dragon Fang or whatever improves Dragon moves would be nice to strengthen Dialga's Dragon Pulse and Roar of Time (if you teach it again.) And I'd give Palkia something to increase the Stab in its physical moves.
I love the team though, especially as there are moves there which definitely counter most types, and cover the types which may be hard to take down. Hope I was useful :)