Tank damage kinda did get nerfed actually as much as people think it 'completely stayed the same'.
WAR lost 5% from deliverance on top of the passive crit buff it provided.
PLD lost 50 potency on every auto attack (remember roughly 30% of your damage is coming from auto attacks)
DRK lost DA on the soul eater combo which is was mostly where thier DA went when Carve/Bloodspiller couldn't be used.
Compared to SB each tank did about roughly 12% of a savage boss's hp over the course of an entire fight. This leads to about 24% in total done by the tanks.
In ShB that number has changed to 11% meaning tanks lost an overall contribution of damage to the boss of 2% of their role. DPS largely remained about the same with their contribution, but healers so far seem to have spiked to almost 10% each for boss contribution. This means the overall raid contribution of tanks got moved to healers which is odd because SE has said multiple times leading up to ShB with the changes to healers that they wanted healers to heal more. The contribution of tanks have gotten low enough for players that Healers are starting to get priority in many groups of gear over tanks because they have to contribute more to the raid group than a tank does.

Tank damage overall needs to get buffs to bring it back to about 12% of group contribution in damage so healers aren't forced to do more work than normal, because keep in mind, this is the first raid teir of the expansion, which means they normally nerf the raid HP of bosses by about 10% (there is an interview saying they made it 15% this tier) which means Tank importance of contributing in damage will be less impactful going further and more focus on other roles making it up.