Hmmm.... Just taking a peek at what you need, I could probably provide a few of those (if not all besides the legendaries.) for no charge at all. I'll just need to check my diamond. (Sorry for a "maybe" post, my game is across the house.)
Edit: Yep! I have all but Seviper on my Diamond! (Well, I DO have seviper but it is shiny and my last one.) Problem: I don't know how you feel about this but the five I do have are NN'ed. Is it okay?
(Corsola: Coveda, Castform: Cally, Crawdaunt: Crab, Mightyena: Mia, Linoone: Rika)
If you still need them, that is.