Cobalion-EX warrants an inclusion imho. It can make dents in opposing pokes for one energy and potentially undo their progress via the special energy attachments that happen before Giratina gets set up. Helps in the mirror match (again due to the first attack), and the second attack can come in...
I'd still include 4 DCE, it's really important for Yveltal's damage output, especially since so many megas are making an appearance. You could probably cut down on 2-3 of each type of energy to make room.
Thoughts on a Metal variant with a Bronzong line and some Aegislash EX? Bronzong can reduce dependency on mega turbos when under item lock. and it can even retrieve energies that were discarded from crushing hammer and flare grunts. Aegislash can tank hits in this special-energy infested...