As for Storm Procs: This is just my opinion.
Storm Cell & Cat 5. I use Sudden Impact's KB to KD. Storm Blast is more stationary then most sets. So no point in scatter shit everywhere.
Chain Lighting: Depends on the AT. But usually the AT Set with bonus damage proc. In case of Sentinel the chance opportunity. Defender: Either Heal or Absorb. More targets more odds.
Blaster: your Defiant Barrage set in Hailstones.
Corrupter: Scourging Blast sin Hailstones
Defender: Depending what is needed, but either Apocalypse, Winter's Bite, or other Defender set not in Chain Lightning. in Hailstones.
Sentinel: Sentinel's Ward.
Beyond that, what ever else suits your tastes or build needs. I personally run Hailstones, Storm Cell, Chain Lightning and either Direct Strike or Cloudburst and Cat 5. For my Storm Builds. Depending on secondaries, those 5 powers are 6 slotted with recipes that will overall help the build. But again that's me and how I play. But if I need more slots cuz of secondaries. I usually will just 3 slot Hailstones and move set planned for it to Direct Strike or Cloudburst. Then 3 slots in Hailstones with Thunderstrike. The 3 pieces with Acc in them.
I try keep movement down and tend to use Chain Lighting like AoE Snipe(ish). To pull stuff towards the Storm Cell & Cat 5 area I set. I know, Storm Cell moves, but it's slow.