I feel like dragon types NEED a basic energy, or they need to either A. Only use one type or B. Use colorless. Dragons have a disadvantage as almost no other card in format required two energy types, even cards like stunfisk that uses lightning and abamasnow only use one type, even though they are another type themselves. There's a reason the only dragons played are ones that are too obvious like black kyurem in blastoise.... scratch that. That's the ONLY dragon that is commonly played. I feel like dragons either need to consistently actually be better cards than other pokemon (see black kyurem) or they need to use only 1 type of colored energy.
Dragons have been an incredibly balanced card type since they have come out and have seen a lot of playability, which means their energy requirements aren't too cost prohibitive, or too hard to achieve to make them playable.
Just a look since last fall:
Altaria DRX - Sees play with Garchomp, which has been a Tier 2ish deck since its inception.
Rayquaza EX - Lots of success in RayEels, some in Rayboar.
Garchomp DRX - Played with Altaria, as well as with Landorus EX and Terrakion.
Giratina EX - Saw play in Hydreigon/Darkrai as a tech.
Hydreigon DRX - Tier 1 deck for Fall Battle Roads, Tier 2 ever since, and stronger now with the release of Bangle and Virizion.
Rayquaza DRX - Saw play in Rayboar/Rayeels. $50 card before it was reprinted in Dragon Vault because of the advantages it brought to RayEels.
So just in the first set that introduced Dragon type Pokemon, we had six cards that made their way into competitive play.
Moving forward:
Kyurem DRV - Potential non-EX dragon counter for Blastoise if you were already running Psychic for stuff like a tech Cresselia during cities.
Black Kyurem BCR - RayEeels/Blastoise counter for Blastoise decks.
Black Kyurem EX BCR - Used in Klinklang during cities to cleanup after a Darkrai snipe or Dual Splash with Kyogre, hitting for 150.
Black Kyurem EX PLS - Black Ballista, main attacker in Blastoise.
That's a lot of good Dragon cards for one year of releases.
As far as Plasma Freeze goes, Latias EX has a unique ability, Dragonite provides trainer lock, which is unique, and Kingdra can rack up a ton of damage and spread. With Plasma Blast, we are given Dialga EX which not only mills, but is also our first colorless dragon counter, meaning it can be slipped into prettymuch anything to counter opposing dragons with ohko's. We also get Haxorus that causes auto-KO Of Plasma Pokemon.
So not only is there plenty of dragon type cards that have already proven to be worthy of the competitive game, there are also quite a few that haven't broken out yet which have unique effects and attacks that could potentially do well in the future.