Yveltal isnt a hard match up without Raichu. Just play smart and it wont be too bad. I usually win vs Yveltal with VirGen with Roserade and Abomasnow. I found that playing aggressive early on seems to work. Focus down the energy and its not too bad. Red Signal out the trubbish if there isnt anything too threatening. Turn 2 Muscle band Emerald slash takes out Sableyes or does just enough damage to allow Genesect to knock it out Yveltals with Megalo Cannon. Darkrai is the only annoying factor of that deck, having 180 HP.
I found with Raichu, that match is just laughable. You can knock the rest of the pokemon out pretty easily with Genesect. The moment they try to respond with Yveltal, Raichu comes out and its over.