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I believe that it really just depends on your needs to either get rid of HJK or Drain Punch but you should definitely not have both. I run Drain Punch with my BU set but you could use HJK for more power if you so desire.
I seem to have just noticed this but four of your pokemon's abilities allow you to negate the effect of four different types which is pretty dang handy.
Serperior
Wouldn't it also be a good idea to maybe slash in Giga Drain for the last move slot to give a decent recovery option? They gave it a boost in power from Gen 4 so it would also be more enticing for attacking options.
I was thinkin of a zuru set that went somethin like this.
ability: overconfidence
item: Muscle Band/left overs
nature:impish
moveset: bulk-up, drain punch, payback, dragon tail
ev's: 252 HP 252 Spec Def 4 Atk