Honestly I'm not sure what's funnier, the fact that they're now looking for stuff like that or the fact that there's probably nothing I can do to convince them it's not me.
That Warden set bonus works out to be a rough -15% incoming damage reduction that you almost always have up. It's not a bad set bonus by any means.
Why? If you've buffed every other tank to the level of Captains you don't need to adjust Captains because that's the new baseline. The whole point of nerfing Captains is that Captains are the single biggest outlier and thus bringing them back into line is less work than anything else since it mostly just involves neutering their support abilities whilst in yellow. Nerfs are not inherently bad and buffs are not inherently good, they're just two ways to accomplish the same goal.