1. How does this card stand on its own?
Terrakion EX is a beast, point blank. His massive 180 HP let's him stand up to anyone, just like most EX's. Weakness to Grass Pokemon isn't that bad, Shaymin EX will be the worst thing for Terrakion EX, but then again, Shaymin is easily KO'd by, well, most attackers, so he won't be a problem. As for the three retreat cost, it's Terrakion, he can handle it.
Terrakion EX's attacks:
[F][C] Rock Tumble: 50 This attacks damage is not affected by resistance.
This is your standard hit for medium damage attack, nothing special, but it will affect CMT, since Tornadus EP can get KO'd quicker and easier.
[F][F][C] Pump Smash: 90 damage. Choose 2 Basic Energy cards from your hand, then attach them to your Benched Pokemon in any way you like.
Finally, energy accelaration for Fighting types that isn't Electrode Prime. Along with a solid 90 damage, 1-2HKO's on anything in the meta, you have the ability to attach two basic energy cards from your hand to anypokemon in anyway you like, pretty good I'd say.
2. What role does/could this card have in the metagame?
Can you say Stampede? If not, you're going to need to learn how. With decks that are weak to fighting controlling the meta after Dark Explorers (Let's face it, we all know it's gonna happen) the Tetrakion deck gains it's most powerful ally ever, another Terrakion. Terrakion EX is going to speed up the build of the Benched Terrakion, making it less costly to do 90 damage each turn. As for other Fighting Decks, I see Machamp Prime (if still in format) making a comeback. Hey, maybe Conkeldurr could make an appearance, with Terrakion EX to help set him up, Conkeldurr could abuse his Craftsmanship ability to with stand hits from just about anything. Only problem with these two decks is that broken genetic freak Mewtwo EX.
3. Give it a rating out of 10:
For the card, as an EX, it has great HP, a medium level attack and a great second attack, pretty good weakness, no resistance and 3 retreat, I'd give this card a 7/10. As for the artwork, the non-full art illustration is incredible, and the Full art looks down right menicing. So for artwork, I give it a 8. Overall. Terrakion EX gets a 7.5/10.