Please tell me, how the hell do you manage to win constantly against Garchomp/Altaria? Garchomp is faster, it kills the Hydreigon Basics and the Hydreign itself everytime. And without the Hydreigon, you cant heal efficient with maxpotion...
On paper it comes down to persuasive arguments. :lol:
There is a slight chance your average Dark Trance deck can come out swinging right away; namely with some well timed discards and multiple Dark Patch. Silly as it sounds, let us realize that Altaria/Garchomp can
never hit had before the deck's second turn.
Next consider targets; if you're busy KOing members of the Hydreigon line, you're taking single Prizes and
ignoring Darkrai EX (or any other attackers in the deck). The Dark Trance player will be laughing all the way to the win if you aren't careful; sure they can't pull the Max Potion trick, but unless you've got a way to boost damage to 200 or to 180 and discard Eviolite, the average Darkrai EX is getting two attacks.
That's enough to take down the first Garchomp and set the second up for a OHKO (or KO it if you aren't Evolving Gible fast enough). Likewise it can set up a pair of Altaria (or an Altaria and a Swablu) for a double KO over the course of two turns. If someone is really gutsy, and runs a clutch Dark Claw, you could really see some craziness happen; 110 to the Defending Pokemon and 30 to a Benched Pokemon is enough to set up Garchomp itself for two KOs in one turn.
Altaria/Garchomp must set-up quickly, cleanly, and never stop rebuilding itself, because by its nature it will almost constantly be losing a Pokemon each turn. This does not make it bad, but at least on paper we now see why Dark Trance decks aren't having a hard time with it. Remember that a nearly KOed Darkrai EX with at least one Darkness Energy attached can retreat for free to the Bench, then have Max Potion dropped on it. Even if that is only a stall tactic, Garchomp may not be able to afford that.
Since Darkrai EX needs
dark::dark::dark
to attack, but also is likely to run Dark Patch, you never know when suddenly the Dark Trance deck will be an Energy attachment or two ahead. The Dark Trance decks I see aren't running heavy on the Special Energy cards (or the splashed in attackers that would need them); a significant difference from Klingklang and vital here. This means Mach Cut isn't protecting Garchomp from a retaliatory hit and another Darkrai EX can be building on the Bench.
tl;dr: Focus too much on Hydreigon (and friends), and you'll face a steady stream of Darkrai EX (and possibly other attackers). Don't forget that setting up a Stage 2 and a string of basic Pokemon is easier than setting up a Stage 2 and a bench full of Stage 1 Pokemon.