3 Heads, 2 Sides and 1 Powerhouse
Hydreigon @ Life Orb
EVs: 4 Att, 252 Sp.Att, 252 Speed
Back in the days where Earth Power and Dark Pulse were not move tutor, I personally used this Mixed-Sweeper set in-game.
Draco Meteor is STAB max power possible.
Fire Blast for steels
Crunch is for special walls
And U-turn is to switch out while weakening my foe.
Other options for this set:
-Choice Scarf can be used instead to make it faster.
-For some reason, I still feel crunch is better than dark pulse. I think it's because majority of ou pokemon weak against dark has lower def than sp.def.
-Maybe give more attack ev?
-Earthquake/Earth Power for heatran