Darkrai does look to be a Technique character. It's gimmick seems to be based on creating illusion doubles of itself, teleportation, and general manipulation of darkness (creating shockwaves, projectiles, and traps). A lot of its attacks also look to stun, such as illusion doubles that explode and an aerial attack.
Entry animation is what you'd expect for Darkrai, it rises from the shadows, at first hidden in a shadow cloud with its visible eye glowing. Victory animation is more darkness manipulation, creating what I can best describe as four darkness tendril batches.
And its Burst Mode takes you to a nightmare dimension filled with odd looking portraits and dark tendrils. Darkrai creates more portraits behind it and Darkrai-like hands reach out of them and grab the opponent Pokemon. Darkrai then becomes a darkness monster, gather the entire dimension into an orb around the opponent Pokemon (who's being pummeled by the hands), and then crushes it. Darkrai be like "Welcome to my nightmare, now SUFFER".
As for design Darkrai looks like Darkrai, guess there's really nothing they could do with its design as its just a mass of darkness.
Overall it looks great!
Let's see, that's 1... 2.. 5 mentions of "darkness" not counting variations of Darkrai's name.