Lose Slaking. The others are OK, though I have to admit I never had much luck with Rejice. My 104-in-a-row team was:
Flygon (starter), Male
Earthquake
Crunch
Fly
Dragonbreath
@Shell Bell
Milotic, Male
Ice Beam
Toxic
Confuse Ray
Recover
@Lum Berry
Skarmory, Female, Sturdy
Drill Peck
Steel Wing
Spikes
HP Fighting
@Leftovers
I found I could deal with Registeel with previous teams, but kept falling eventually to OHKO. 300 pokemon battles is a lotta time for bad runs of luck to happen, and a Sturdy type proved the edge I needed. The immunity to Poison on Skarm and immunity to Electric on Flygon proved very useful. Fly is not a bad move vs computer opponents - they don't react intelligently to it, and it can be used to minimise explosion chances.