It's not even working as intended. He is flat out saying it is NOT working as intended, and without question migitragion tanks are far more useful on raids. He flat out is telling the community that on the current raids DO NOT USE SHADOW TANK because bosses do all force / tech damage (something we have known for months).
And then he says 1) no, we are not going to change that. We are going to let them contiune doing all force and tech damage and
2) we are going to nurf you anyway, so you suck even more, and we have no concerns at all about this.
I don't know what you read, but that is not what he said at all. This is what he said in regards to potentially changing the way bosses do damage and the way that damage is avoided/mitigated:
"Not all channels of survivability can be balanced for every boss encounter, which is why tank survivability is measured against a norm, and why we're going to be pushing harder to hit that norm in the future - either through tweaks in boss damage or tweaks to the way shields work
He clearly said it is a known problem that they are going to be working on.