Dusknoir is quite a sturdy fellow. Pursuit is no threat if it just doesn't switch, during which time it can just burn the user (primarily T-Tar/Weavile) and Pain Split back to health there or later on. Its high defenses and lack of weaknesses make it a potential counter to a lot of pokemon (it even gets a priority move) and it has the versatility to basically just "fill in holes" for any half-finished team needing one or two more members. It's also a fantastic wall against Rapid Spinners.
And Blissey stops many set-up special attackers as well. CM Celebi is a worry to Blissey not in itself but because it can BP the boosts off to somebody more dangerous. Likewise, PZ is dangerous because it's one of the few strong enough that can punch through Blissey's SpDef (with Adaptability-STAB Normal). Azelf, despite its quick setup, is ruined by Blissey because it can switch in easily and either keep up defensively with Calm Mind or simply cripple Azelf with status.
To add to the physical argument, there's a very good reason most of the metagame's threats are physical. There are just more physical moves to utilize: EQ and Stone Edge are TMs, Close Combat or a similar attack (Sky Uppercut, HJK, Cross Chop) are learned by pretty much anything that could make use of them except poor ol' :@. By contrast, Earth Power and Aura Sphere are highly exclusive and there's no good special Rock attack at all (Power Gem is terrible and even more exclusive than EP/AS). Pursuit became physical and most of the pokemon that learn it are heavy physical hitters. The Sandstorm buff helps a purely physical type (Rock). That's before you even get into Blissey, the 700+ HP, 300+ SpD pokemon with a recovery move and an anti-status trait that is weak to absolutely nothing special but Aura Sphere, which we've already covered as very exclusive; there's no comparable pokemon with that kind of catch-all physical endurance not to mention recovery and status absorption.
And this is an interesting thread, indeed.
