Mienshao isn't a good scout as it used to be since B2/W2. Genesect is the better option, IMO, because of its fantastic coverage:
-U-turn
-Ice Beam
-Thunderbolt/Bug Buzz
-Flamethrower/Bug Buzz
Nature: Hasty/Naive
EVs: 8 Atk/248 SAtk/252 Spe
Item: Choice Scarf
or
-U-turn
-Ice Beam
-Flamethrower
-Bug Buzz/Thunderbolt
Nature: Hasty/Naive
EVs: 4 Atk/252 SAtk/252 Spe
Item: Focus Sash/Expert Belt
or
-Bug Buzz
-Ice Beam
-Thunderbolt
-U-turn/Flamethrower/Giga Drain
Nature: Mild/Rash
EVs: 4 Atk/252 SAtk/252 Spe
Item: Choice Specs
or
-U-turn
-Iron Head/Zen Headbutt
-Flamethrower
-Ice Beam/Explosion
Nature: Hasty/Naive
EVs: 252 Atk/4 SAtk/252 Spe
Item: Choice Band
The forced Rash nature makes Calm Mind a not-so-appealing option on Raikou. If you want to use Calm Mind, go with these:
-Calm Mind
-Thunderbolt
-Shadow Ball
-Hidden Power (Ice/Fighting)
Nature: Timid
EVs: 252 SAtk/4 SDef/252 Spe
Item: Life Orb
or
-Substitute
-Calm Mind
-Thunderbolt
-Hidden Power (Ice/Grass)
Nature: Timid
EVs: 128 HP/76 Def/52 SAtk/252 Spe
Item: Leftovers
But then again, Jolteon or Rotom-W are better options over it due to their better speed or bulk, respectively:
Jolteon:
-Thunderbolt
-Volt Switch
-Hidden Power (Ice/Grass)
-Signal Beam/Shadow Ball
Nature: Timid
EVs: 252 SAtk/4 SDef/252 Spe
Item: Life Orb/Choice Specs
Ability: Volt Absorb
Rotom-W:
-Volt Switch
-Hydro Pump
-Will-o-Wisp
-Pain Split/Hidden Power (Ice)
Nature: Modest
EVs: 184 HP/4 Def/144 SAtk/176 Spe
Item: Leftovers
or
-Volt Switch
-Hydro Pump
-Thunder Wave/Will-o-Wisp
-Pain Split
Nature: Calm
EVs: 248 HP/28 SAtk/232 Spe
Item: Leftovers
or
-Volt Switch
-Hydro Pump
-Hidden Power (Ice)
-Trick/Thunderbolt
Nature: Timid
EVs: 4 HP/252 SAtk/252 Spe
Item: Choice Specs/Choice Scarf
Roost is better off in bulky QD Volcarona; if you want to keep Roost, use the EV spread of 240 HP/216 Def/52 Spe with a Bold nature. If you want to keep your current EV spread, replace Roost with Hidden Power Ground or Rock.
While Swords Dance Haxorus might seem tempting at first glance, it's a bit slow and can be revenge killed easily, so Dragon Dance Haxorus can be considered. Outrage is the better option over Dragon Claw, as the latter move misses out on some key OHKOs. You can also consider Magnezone over Raikou/Jolteon/Rotom-W as a way to give Haxorus a setup opportunity by eliminating Steels:
-Substitute
-Thunderbolt
-Hidden Power (Fire/Ice)
-Flash Cannon/Charge Beam
Nature: Timid
EVs: 36 HP/252 SAtk/220 Spe
Item: Leftovers
Ability: Magnet Pull
or
-Thunderbolt
-Volt Switch
-Flash Cannon
-Hidden Power (Fire/Ice)
Nature: Timid (Choice Scarf)/Modest (Choice Specs)
EVs: 4 HP/252 SAtk/252 Spe (Choice Scarf) or 148 HP/252 SAtk/108 Spe (Choice Specs)
Item: Choice Scarf/Choice Specs
Ability: Magnet Pull
Gliscor absolutely needs Earthquake as its offensive move, as the lack of STAB and power hurt. Ice Fang is totally optional. The preferred EV spread now is 248 HP/188 Def/72 Spe so that Gliscor takes a bit less damage from Stealth Rock.
Don't use Earthquake on Terrakion; it has redundant coverage with Close Combat. Rock + Fighting already have good coverage, so using Rock Polish + Swords Dance isn't a bad idea. Rock Polish allows Terrakion to outspeed most offensive Pokemon against offensive teams, while Swords Dance lets Terrakion break stall teams. Life Orb, Air Balloon or Rock Gem are also the preferred options over Lefties. Life Orb is pretty much the standard item for sweeper sets, Air Balloon lets Terrakion temporarily avoid Earthquake and Rock Gem gives Stone Edge a bit more bite against physically defensive Pokemon, but only once.