I would replace Salamence with CB scizor. Scizor's priority in hail is pretty effective. It's mostly a hit and run pokemon so it won't be affected by the hail as much as other pokemon. Volturn will allow you to deal with some offensive threats a little bit easier, especially with hail cancelling out most pokemon's leftovers.
In addition I would give Rotom Def EVs where you put them in spdef. Although you give Genesect a spatk boost, you have kyurem to handle most sets other than CB and those with flash cannon. and flash cannon variants are handled by rotom :].
My youtube channel
[Pokemon Narrations, Let's Plays]
VM me for OU/UU rates.
wish i could change my username to chimpact :[