[SIZE="a"]Hello I am making a hydreigon darkrai deck. I want to make this deck like a klingklang ex with alot of ledgendaries. Will this be good? Here are the pokemon lines
1 terrakion ex
1 groudon ex
1 mewtwo ex
1 Kyurem ex
1 mew ex[/SIZE]
The only EX's you should run in Hydreigon are multiple Darkrai, and maybe 1 Giratina EX or 1 Shaymin EX. You really want to stick with Blend GFPD over prisms because 1 big issue is if a prism moves to an evolved pokemon it effectively gets stuck. Plus you want consistent access to the specific energy type you need to move around, and running too many techs can leave you more vulnerable if you can't get the setup.
And if someone decides to go happy with the enhanced hammers, you don't want a bunch of dead pokemon in play.