Dark / Storm -- Build ideas?

I'm curious, what do people consider the "Must haves" of this set?

I have been dying to try a /storm - and I have never played a defender (Although I do have 2 controllers @ 50).. I remember playing Dark before, and liking the set becuase of the great -tohit debuffs, (And I liked the effects)

What should I be tryign to slot for general leveling, grouping, team support - and @ 50, if I slot for damage, is that a good idea? Can I get good dps from a defender?

Thanks for the help!

I wrote a guide on this powerset combo. It's up in the guides section if you'd like to check it out.