DKs are OK still even in 5.3. On my holy pal/dk team I beat 2170 MMR team this season (with me playing the healer too). They lost 60 points off of me because I'm keeping it low around 1600 so I can cap easily. I'm pretty sure in 5.4 DKs can hit 2k+ easy. It's all about popping all cooldowns a killing one healer in the first 30 seconds.