To be fair, it depended upon the tank class and the encounter. For Guardians, you could pick a DPS build and not have to worry about dying, unlike DK's for example... so as long as you had enough survivability for your group, bears could just go DPS-mode with gearing. There were also some fights where tank damage was nuts, especially in the early weeks of progression when compared to DPSers, and gearing choices to could make a huge difference in damage output with negligible effect on survivability. There were also fights where damage was not important, just execution and survival.
Out of all the SoO encounters, I'd say Siegecrafter Blackfuse was the fight where there was a conscious decision about what damage a tank could do regardless of how survivable they were. I suppose technically the last bosses in SoO had a similar feel for tanks, since maximizing damage was insanely important early in progression, forcing tanks into playing like a DPSer. While proportionally to raid size, the amount of damage a tank does overall is smaller in a 25man compared to the rest of the roster, it was still very important to the execution of the encounters where occasionally seconds count (such as heroic Garrosh).
Moving into WoD, where *hopefully* tank damage is fairly even across the board in most situations, the amount of damage a tank does will still have some impact. Since we'll have less customization with our gear, the gap between gearing for survivability and gearing for DPS should get smaller if designed properly. As a long-time tank, I've rather missed gearing for survivability since MoP made that mostly pointless, but I don't fancy returning to where tank damage is nonexistent and trivial at best. We also have to keep in mind that tank survivability and damage is likely balanced around the average player, so skilled players can take advantage of any wiggle room in the survivability or DPS department.