Miltank: Get him out of the lead spot, leading with a heal beller wont work, use Raikou as the lead.
Raikou: Get rid of zap cannon for water HP or reflect, or drop for Jolteon or Zappy.
Quagsire: A set I used at one time, I don't find it that great anymore. I don't know much about Quagsire, but maybe Earthquake, safeguard, haze, ancientpower/swagger/whatever. On him and Raikou, drop the move boosters for something better.
Heracross: I don't like heracross at all, and quick claw wont help much(If any). Try Rock HP over return.
Shuckle: Way too much setup time. I don't like the idea of toxic if u use a paralyser, otherwise, go with the Toxic trapper. If you switch Raikou for a better paralyzer, maybe Double team, rest, defense curl, rollout, but I don't really know how it would work.
Espeon: This set sucks. Bite is probably better anyway with Espeon's good speed & SA. Use psychic, bite/attract, charm, morning sun.
Overall: Could work OK, but some of the movesets need help.
How to ruin a Snorlax: