you unfortunately need to pass over a dragon (garchomp, personally) with it from a HG/SS tm
if you want a dark pulse dieno to breed with, i'd be happy to trade you one
I'm almost positive that Garchomp can't learn Dark Pulse even in 4thGen
In fact i'm pretty sure that the only two pokemon that can learn it and and parent a Deinos are Gyarados and Serviper.