One unboosted attack and no status just begs the opponent to Taunt or set-up on you, you should know this as a competitive player.
Since you can only have one attacking type, don't bother with different types of counters. Only psychic means a dark-type walls you, only water means a water-absorber or bulky water walls you, only grass knot means that Mence and other 4x grass resisters wall you, and only Shadow ball means that any normal type walls you.
No Blissey would ever try to wall such a piddly attacker as this. I imagine the most common switch-in would either be Weavile or Heracross and you can't carry more than Psychic. Take this one back to the drawing book.
If he maxed out defense (ie, BOLD) and got rid of reflect, he could have Psychic and Thunderbolt ... that'd make the set far more effective. The only Dark Types that resist electric are Shiftry and Cacturne