An offense based team, even one that implements explosion as its prime tactic does not and should not sacrifice all of its defense for offensive capability. Reflect on Metagross is about the only thing the team has for support and the move does not have a big enough impact on the other pokemons survivability to justify the teams weakness, especially if a swampert or another such pokemon is on the opposing team preventing Metagross from getting into play effectively. More EVs should be put into defense for all pokes even the weakest ones - in this case a little defense will go much farther than a lot of attack.
In terms of moves, I would suggest the following. Place Giga Drain onto Gengar in the place of the move of your choice (I would suggest Will-O-Wisp). Take the bulk of Snorlax's attack evs and put them into defense and a little into special defense and replace Return with Rest as Selfdestruct is going to be an autoko on most pokemon (bulkier ones that survive will be killed by other pokemons offensive movesets). The stab move is unnecessary in this case as Snorlax is trying to tank instead of sweep. Change Metagross's nature to +Defense or swap the evs around putting in a lot more defense (whichever is statistically most beneficial) as it is your only answer to a strong normal/flying type STAB attacker. I would not suggest changing Alakazam or Dugtrio as they are obviously not built to be defensive in the slightest and they play together nicely as well as fitting the role of sweeper the best. Your Raikou looks decent to me although there's something about it that bothers me but I can't place my finger on it.