Despite lacking immunity to sandstorm, Blissey is frequently seen on defensive sandstorm teams because it's unrivalled as the best special wall in the game. Blissey can sponge special attacks, spread status around, and heal your own team's status with Heal Bell. Blissey can also provide Wish support for the team. This is very helpful because a lot of the other walls that do well in sandstorm (Registeel, Donphan, Regirock, Forretress, and others) do not have reliable recovery of their own. The easiest way to counter Blissey is with strong physical attacks. Choice Dugtrio does a great job, as it can trap Blissey and 2HKO it with Earthquake. Other good counters include Machamp and Infernape, though Infernape needs to watch out for the occasional Thunder Wave.