He's not saying it's always the tanks fault, he's saying that it isn't always the DPS' fault.

If I'm in BWD throwing nasty at Arcanotron while standing on top of a goo puddle (the good kind that boosts your damage, I forgot what they're called) in the middle of a Bloodlust when Magmatron is activated, then I need to keep in mind that I'm turning a LOT of damage at the moment and need to give the tank a sec to hit it once or twice. If I dont do that and I rip the boss across the room before the tank can get it's attention, then it's my fault. However, if the tank who is supposed to be picking him up isnt paying attention and is on the wrong side of the room rather than standing next to it with his finger hovering over Shield Slam, then it's his fault.

However, if you're 2 minutes into Baleroc and you're creeping up on the threat table and in danger of pulling, then there's something seriously wrong and it IS the tank's fault. Threat has been neutered to the point that if a DPS just plain outthreats a tank, then the tank is either 1) Vastly outgeared (333's and leveling greens against FL gear) or 2) doing something horribly wrong.